Virtual image display apparatus

ABSTRACT

An advantage of some aspects of the invention is to provide a virtual image display apparatus in which occurrence of luminance spots is suppressed to improve efficiency of use of illumination light. In the virtual image display apparatus of the invention, an optical-directivity changing section forms a non-uniform distribution concerning the directivity of image lights GL emitted from an image display device. Therefore, even when an angle of a light beam emitted from the image display device and effectively captured into the eye EY of an observer is substantially different depending on a position of the image display device, it is possible to form the image lights GL having directivity corresponding to such an angle characteristic of light beam capturing. It is possible to suppress occurrence of luminance spots to improve efficiency of use of illumination light.

BACKGROUND

1. Technical Field

The present invention relates to a virtual image display apparatus suchas a head-mounted display worn on the head and used.

2. Related Art

In recent years, as a virtual image display apparatus that enablesformation and observation of a virtual image such as a head-mounteddisplay, various virtual image display apparatuses of a type for guidingvideo light from a display element to the pupils of an observer with alight guide plate are proposed. As the light guide plate for suchvirtual image display apparatuses, there is known a light guide platethat guides video light making use of total reflection and reflects thevideo light on plural partial reflection surfaces arranged in parallelto', one another at a predetermined angle with respect to a principalplane of the light guide plate and extracts the video light to theoutside from the light guide plate to thereby cause the video light toreach the retinas of the observer (see JP-T-2003-536102 (the term “JP-T”as used herein means a published Japanese translation of a PCTapplication) and JP-A-2004-157520).

In the virtual image display apparatus explained above, for example,light beams from upper and lower ends of a longitudinal cross-section ofthe display element need to be made incident on the pupils of theobserver at a large tilt angle corresponding to an angle of view. Thelight beams are emitted from the display element at a relatively largetilt angle. A light beam from the center of the display element is madeincident on the pupils of the observer without being tilted from thefront. Therefore, the light beam is emitted in the front direction fromthe display element. When the display element is obtained by combining,for example, an illuminating device and a liquid crystal panel, ingeneral, a distribution of light of the illuminating device issubstantially uniform in a screen having an intensity peak in adirection perpendicular to the liquid crystal panel. Therefore, even ifluminance is high in the center of an image where the tilt ofillumination light is small, luminance falls at upper and lower ends ofthe image where the tilt of the illumination light increases. Thiscauses luminance spots of the image. In this case, the illuminationlight is not effectively utilized at upper and lower ends of the screen.It can be said that efficiency of use of the illumination light falls.

On the other hand, concerning a light beam from a lateral cross-sectionof the display element, an angle direction in which the light beam iscaptured by the light guide plate and used for display substantiallytilts from the front direction of the display element according to alateral position of the light beam. Therefore, a phenomenon could occurin which, even if luminance is high in a lateral position where the tiltof the illumination light is small, luminance falls in another lateralposition where the tilt of the illumination light increases. In thiscase, the illumination light is not efficiently used and belt-likeluminance spots extending in the longitudinal direction occur.

SUMMARY

An advantage of some aspects of the invention is to provide a virtualimage display apparatus in which occurrence of luminance spots issuppressed to improve efficiency of use of illumination light.

According to an aspect of the invention, a virtual image displayapparatus includes: (a) an image display device that forms image light;(b) a projection optical system that forms a virtual image with theimage light emitted from the image display device; (c) a light guidedevice including a light incident section that captures the image lightpassed through the projection optical system into the inside of thelight incident section, a light guide section that guides the imagelight captured from the light incident section using total reflection onfirst and second reflection surfaces extending while being opposed toeach other, and a light emitting section that extracts the image lightpassed through the light guide section to the outside; and (d) anoptical-directivity changing section that changes the directivity of theimage light emitted from the image display device and forms anon-uniform distribution. The directivity of the image light means thatthe luminance center of the image light emitted from the image displaydevice deviates to a specific direction (specifically, a specific tiltangle and a specific azimuth).

In the virtual image display apparatus, the optical-directivity changingsection forms a non-uniform distribution concerning the directivity ofthe image light emitted from the image display device. Therefore, evenwhen an angle of a light beam emitted from the image display device andeffectively captured into the eye of an observer is substantiallydifferent depending on a position of the image display device, it ispossible to form image light having directivity corresponding to such anangle characteristic of light beam capturing. It is possible to suppressoccurrence of luminance spots to improve efficiency of use ofillumination light. The angle characteristic of light beam capturingoccurs depending on, for example, specifications of the projectionoptical system and the light guide device. For example, the tilt tendsto be larger on a peripheral side than a center side of a display areaof the image display device or larger on the center side than theperipheral side of the display area.

In a specific aspect of the invention, in the virtual image displayapparatus, the optical-directivity changing section bends, concerning afirst direction, light at a different angle according to a position ofthe image display device. In this case, an angle characteristic of thelight can be adjusted according to bending of the illumination light andthe image light corresponding to the position in the first direction.Even if, in the angle characteristic of light beam capturing, the tiltlocally increases in a cross-section in the first direction, it ispossible to suppress luminance spots to improve light use efficiency.

In another aspect of the invention, the optical-directivity changingsection bends, concerning a second direction perpendicular to the firstdirection, light at a different angle according to the position of theimage display device. In this case, an angle characteristic of the lightcan be adjusted according to bending of the illumination light and theimage light corresponding to the position in the second direction. Evenif, in the angle characteristic of light beam capturing, the tiltlocally increases in a cross-section in the second direction, it ispossible to suppress luminance spots to improve light use efficiency.

In still another aspect of the invention, in the optical-directivitychanging section, a light distribution characteristic, which is an angledistribution of directivity, is different concerning the first directionand the second direction. In some case, the angle characteristic oflight beam capturing is different in the first direction and the seconddirection (e.g., the longitudinal direction and the lateral direction)because of, for example, the structure of the light guide section. Evenin such a case, it is possible to suppress occurrence of luminance spotsover the entire screen.

In still another aspect of the invention, the image display deviceincludes an illuminating device and an image-light forming section thatcontrols light from the illuminating device and forms image light.

In still another aspect of the invention, the illuminating deviceincludes a light emitting section and a backlight guide section thatspreads a light beam from the light emitting section in a surface lightsource shape. The optical-directivity changing section is arrangedbetween the backlight guide section and the image-light forming section.In this case, even if a light distribution characteristic of theillumination light emitted from a light emission surface of thebacklight guide section is uniform, a light distribution characteristicof the illumination light made incident on the image-light formingsection can be adjusted to a desired state by the optical-directivitychanging section. It is possible to set the directivity of the imagelight emitted from the image display device to directivity correspondingto the angle characteristic of light beam capturing.

In still another aspect of the invention, the illuminating deviceincludes a surface-light-source-like light emitting section. Theoptical-directivity changing section is arranged between thesurface-light-source-like light emitting section and the image-lightforming section. In this case, even if a light distributioncharacteristic of the illumination light emitted from thesurface-light-source-like light emitting section is uniform, a lightdistribution characteristic of the illumination light made incident onthe image-light forming section can be adjusted to a desired state bythe optical-directivity changing section. It is possible to set thedirectivity of the image light emitted from the image display device todirectivity corresponding to the angle characteristic of light beamcapturing.

In still another aspect of the invention, the optical-directivitychanging section is at least one of a prism array sheet, a Fresnel lens,a diffractive optical element, and a micro lens array.

In still another aspect of the invention, the optical-directivitychanging section is bonded to the backlight guide section or thesurface-light-source-like light emitting section and integrated with thebacklight guide section or the surface-light-source-like light emittingsection. In this case, it is easy to assemble the optical-directivitychanging section in the image display device.

In still another aspect of the invention, the optical-directivitychanging section includes plural area sections for causing illuminationlight from the backlight guide section or the surface-light-source-likelight emitting section to pass such that main directivity directionshaving highest luminance are different from each other. In this case, itis possible to set a light distribution characteristic of theillumination light to an appropriate state for each of the plural areasections.

In still another aspect of the invention, the optical-directivitychanging section includes a prism array having different shapes tocorrespond to the plural area sections. In this case, it is possible toadjust the light distribution characteristic of the illumination lightto a target light distribution characteristic by adjusting a wedge angleof prism elements included in the prism array in the area sections.

In still another aspect of the invention, the first directioncorresponds to a returning direction perpendicular to the first andsecond reflection surfaces of the light guide device and the seconddirection corresponds to a non-returning direction parallel to the firstand second reflection surfaces of the light guide device andperpendicular to the first direction. In at least one of the firstdirection and the second direction, plural peak directions in whichluminance is the maximum are set.

In still another aspect of the invention, in the second direction,plural peak directions in which luminance is the maximum are set.Concerning the second direction corresponding to the non-returningdirection of the light guide device, a tilt angle of the image lightcaptured on the peripheral side of the display area of the image displaydevice does not uniformly tend to be larger than that on the center sideof the display area of the image display device and a tile angle of theimage light captured in positions in the second direction non-uniformlychanges. Therefore, it is possible to reduce luminance spots byadjusting the directivity of the image light concerning the seconddirection.

In still another aspect of the invention, the optical-directivitychanging section is incorporated in or externally attached to theimage-light forming section.

In still another aspect of the invention, the image-light formingsection is an EL display element and the optical-directivity changingsection is arranged, for example, near a light emission side of a pixelportion of the EL display element.

In still another aspect of the invention, the image-light formingsection is a liquid crystal display element of a light-transmissive typeand the optical-directivity changing section is arranged, for example,near at least one of a light incident side and a light emission side ofa pixel portion of the liquid crystal display element. In this case,even if a light distribution characteristic of the illumination lightemitted from the light emission surface of the backlight guide sectionis uniform, the direction of the illumination light made incident on theimage-light forming section and the direction of the image light emittedfrom the image-light forming section can be adjusted by theoptical-directivity changing section. In other words, it is possible toset the directivity of the image light emitted from the image displaydevice to directivity corresponding to the angle characteristic of lightbeam capturing.

In still another aspect of the invention, the light guide section has afirst reflection surface and a second reflection surface that arearranged in parallel to each other and enable light guide by totalreflection. The light incident section has a third reflection surfaceformed at a predetermined angle with respect to the first reflectionsurface. The light emitting section has a fourth reflection surfaceformed at a predetermined angle with respect to the first reflectionsurface. In this case, the image light reflected on the third reflectionsurface of the light incident section is propagated while being totallyreflected on the first and second reflection surfaces of the light guidesection and is reflected on the fourth reflection surface of the lightemitting section and made incident on the eye of the observer, as avirtual image.

In still another aspect of the invention, the light emitting sectionincludes an angle converting section that has plural reflection surfacesand converts an angle of the image light through reflection on theplural reflection surfaces to enable the image light to be extracted tothe outside. In this case, it is possible to divide a light beam fromthe thin light guide section and extract the light beam in anappropriate direction.

In still another aspect of the invention, the angle converting sectionincludes plural reflection units that respectively have first reflectionsurfaces and second reflection surfaces formed at a predetermined anglewith respect to the first reflection surfaces and are arrayed in apredetermined array direction. The reflection units reflect, with thefirst reflection surfaces, the image light made incident through thelight guide section and further reflect, with the second reflectionsurfaces, the image light reflected by the first reflection surfaces tothereby bend an optical path of the image light and enable the imagelight to be extracted to the outside. In this case, the image lighthaving a large reflection angle propagated through the light guidesection can be extracted on the depth side of the angle convertingsection and the image light having a small reflection angle propagatedthrough the light guide section can be extracted on the entrance side ofthe angle converting section. Therefore, it is possible to display ahigh-quality image in which a luminance fall and luminance spots due tothe angle converting section are surely suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view showing a virtual image display apparatusaccording to a first embodiment.

FIG. 2A is a plan view of a main body section of a first display deviceincluded in the virtual image display apparatus.

FIG. 2B is a front view of the main body section.

FIG. 3A is an exploded conceptual diagram of an optical path concerninga longitudinal first direction.

FIG. 3B is an exploded conceptual diagram of an optical path concerninga lateral second direction.

FIG. 4 is a plan view for specifically explaining an optical path in anoptical system of the virtual image display apparatus.

FIG. 5A is a diagram showing a display surface of a liquid crystaldisplay device.

FIG. 5B is a diagram for conceptually explaining a virtual image of aliquid crystal display device visible to an observer.

FIGS. 5C and 5D are diagrams for explaining partial images forming thevirtual image.

FIG. 6A is a side view for explaining an emission angle concerning thelongitudinal direction of image light emitted from the liquid crystaldisplay device.

FIG. 6B is a graph for conceptually explaining an angle characteristicof light beam capturing concerning the longitudinal direction.

FIG. 7A is a side view for explaining an emission angle concerning thelateral direction of the image light emitted from the liquid crystaldisplay device.

FIG. 7B is a graph for conceptually explaining an angle characteristicof light beam capturing concerning the lateral direction.

FIG. 8 is a conceptual diagram for explaining an angle characteristic oflight beam capturing as a two-dimensional distribution.

FIGS. 9A to 9D are respectively a plan view, a side view, a rear view,and a partially cut-out perspective view for explaining anoptical-directivity changing section for adjusting directivity of imagelight.

FIG. 10A shows a light distribution characteristic on the entrance sideof an optical-directivity changing section.

FIG. 10B shows a light distribution characteristic in the longitudinaldirection on the exit side of the optical-directivity changing section.

FIG. 10C shows a light distribution characteristic in the lateraldirection on the exit side of the optical-directivity changing section.

FIG. 11 is an enlarged longitudinal sectional view for explaining thestructure and functions of the optical-directivity changing section.

FIG. 12 is an enlarged lateral sectional view for explaining thestructure and functions of the optical-directivity changing section.

FIGS. 13A and 13B are respectively a longitudinal sectional view and alateral sectional view for explaining a liquid crystal display deviceand the like incorporated in a virtual image display apparatus accordingto a second embodiment.

FIGS. 14A and 14B are diagrams for explaining a modification of thesecond embodiment.

FIGS. 15A and 15B are respectively a longitudinal sectional view and alateral sectional view for explaining a liquid crystal display deviceand the like incorporated in a virtual image display apparatus accordingto a third embodiment.

FIGS. 16A and 16B are diagrams for explaining a modification of thesecond embodiment.

FIG. 17 is a diagram for explaining a main part of a virtual imagedisplay apparatus according to a fourth embodiment.

FIG. 18 is a partially enlarged sectional view for explaining a virtualimage display apparatus according to a fifth embodiment.

FIGS. 19A and 19B are diagrams for explaining a virtual image displayapparatus according to a sixth embodiment.

FIG. 20A is a sectional view showing a virtual image display apparatusaccording to a seventh embodiment.

FIGS. 20B and 20C are respectively a front view and a plan view of alight guide device.

FIGS. 21A to 21C are schematic diagrams for explaining the structure ofan angle converting section and an optical path of image light in theangle converting section.

FIGS. 22A to 22D are diagrams for explaining a main part of a virtualimage display apparatus according to an eighth embodiment.

FIGS. 23A and 23C are diagrams for explaining a two-dimensionalluminance distribution and a sectional luminance distribution of animage formed by the virtual image display apparatus according to theeighth embodiment.

FIGS. 23B and 23D are diagrams for explaining a two-dimensionalluminance distribution and a sectional luminance distribution of animage formed by a virtual image display apparatus according to acomparative example.

FIGS. 24A and 24B are diagrams for explaining a part of a virtual imagedisplay apparatus according to a ninth embodiment.

FIG. 25 is a diagram for explaining a virtual image display apparatusaccording to a tenth embodiment.

FIG. 26 is a diagram for conceptually explaining a modification of thevirtual image display apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A virtual image display apparatus according to an embodiment of theinvention is explained in detail below with reference to theaccompanying drawings.

A. External View of the Virtual Image Display Apparatus

A virtual image display apparatus 100 according to a first embodimentshown in FIG. 1 is a head-mounted display having an external appearancelike eyeglasses. The virtual image display apparatus 100 can cause anobserver wearing the virtual image display apparatus 100 to recognizeimage light by a virtual image and cause the observer to observe anexternal view seeing through the virtual image display apparatus 100.The virtual image display apparatus 100 includes an optical panel 110that covers the front of the eye of the observer, a frame 121 thatsupports the optical panel 110, and first and second driving sections131 and 132 added to a section extending from an armor to a temple ofthe frame 121. The optical panel 110 includes a first panel section 111and a second panel section 112. Both the panel sections 111 and 112 aretabular components integrally coupled in the center thereof. A firstdisplay device 100A obtained by combining the first panel section 111and the first driving section 131 on the left side on the drawing is asection that forms a virtual image for the left eye. The first displaydevice 100A independently functions as a virtual image display apparatusas well. A second display device 100B obtained by combining the secondpanel section 112 and the second driving section 132 on the right sideon the drawing is a section that forms a virtual image for the righteye. The second display device 100B independently functions as a virtualimage display apparatus as well. The first driving section 131 and thesecond driving section 132 are individually housed in cases 141 forlight blocking and protection.

B. Structure of the Display Device

As shown in FIG. 2A and the like, the first display device 100A includesan image forming device 10 and a light guide device 20. The imageforming device 10 is equivalent to the first driving section 131 inFIG. 1. The light guide device 20 is equivalent to the first panelsection 111 in FIG. 1. Concerning the image forming device 10, a mainpart section excluding the case 141 in FIG. 1 is shown. In FIG. 2A, thesection of the light guide device 20 is an A-A arrow sectional view ofFIG. 2B. The second display device 100B shown in FIG. 1 has a structuresame as the structure of the first display device 100A and is obtainedby simply reversing the left and the right. Therefore, detailedexplanation of the second display device 100B is omitted.

The image forming device 10 includes an image display device 11, aprojection optical system 12, and an optical-directivity changingsection 38. The image display device 11 includes an illuminating device31 that emits two-dimensional illumination lights SL, a liquid crystaldisplay device (a liquid crystal display element) 32, which is atransmissive image-light forming section, and a driving control section34 that controls the operations of the illuminating device 31 and theliquid crystal display device 32.

The illuminating device 31 includes a light source 31 a, which is alight emitting section that generates light including three colors ofred, green, and blue, and a backlight guide section 31 b that diffusesthe light from the light source 31 a and changes the light to a lightbeam having a two-dimensional spread of a rectangular section. Theliquid crystal display device (the image-light forming section) 32spatially modulates the illumination lights SL from the illuminatingdevice 31 and forms image light that should be a display target such asa moving image. The driving control section 34 includes a light-sourcedriving circuit 34 a and a liquid crystal driving circuit 34 b. Thelight source driving circuit 34 a supplies electric power to the lightsource (the light emitting section) 31 a of the illuminating device 31and causes the light source 31 a to emit the illumination lights SLhaving stable luminance. The liquid crystal driving circuit 34 b outputsan image signal or a driving signal to the liquid crystal display device(the image-light forming section) 32 to thereby form, as a transmittancepattern, color image light that is a source of a moving image or a stillimage. An image processing function can be imparted to the liquidcrystal driving circuit 34 b. However, the image processing function canbe imparted to an externally-attached control circuit as well.

The optical-directivity changing section 38 is arranged between theilluminating device 31 and the liquid crystal display device 32. Theoptical-directivity changing section 38 is a deflecting element forcorrecting an angle distribution or a light distribution characteristicof the directivity of illumination light emitted from the illuminatingdevice 31 to an appropriate angle distribution or an appropriate lightdistribution characteristic that takes into account efficiency of use.The optical-directivity changing section (the deflecting element) 38adjusts the directivity of image light emitted from the liquid crystaldisplay device 32 to directivity corresponding to an effective emissionangle range (an angle characteristic of light beam capturing explainedlater) in which the image light emitted from the liquid crystal displaydevice 32 is resultantly made incident on an eye EY of the observer.

In the liquid crystal device 32, a first direction D1 corresponds to adirection in which a longitudinal cross-section including a firstoptical axis AX1 passing through the projection optical system 12 and aspecific line parallel to a third reflection surface 21 c of a lightguide member 21 explained later extends. A second direction D2corresponds to a direction in which a lateral cross-section includingthe first optical axis AX1 and the normal of the third reflectionsurface 21 c extends. In other words, the first direction D1 is adirection parallel to a line of intersection of a first reflectionsurface 21 a and the third reflection surface 21 c of the light guidemember 21. The second direction D2 is a direction parallel to a plane ofthe first reflection surface 21 a and perpendicular to the line ofintersection of the first reflection surface 21 a and the thirdreflection surface 21 c. In short, in a position of the liquid crystaldisplay device 32, the first direction D1 is equivalent to alongitudinal Y direction and the second direction D2 is equivalent to alateral X direction. An effective size H in the longitudinal firstdirection D1 of the liquid crystal display device 32 is smaller than aneffective size W in the lateral second direction D2 of the liquidcrystal display device 32 (see FIG. 2B). In other words, an imageforming area AD of the liquid crystal display device 32 is laterallylong. The first direction D1 is parallel to the Y direction in both ofthe image forming device 10 and the light guide member 21 explainedlater and corresponds to a non-returning direction or a non-confiningdirection DW2 of the light guide member 21. The second direction D2 isparallel to the X direction in the image forming device 10 but isparallel to a Z direction in the light guide member 21 explained laterand corresponds to a returning direction or a confining direction DW1.

The projection optical system 12 is a collimate lens that changes imagelight emitted from respective points on the liquid crystal displaydevice 32 to a light beam in a parallel state. The projection opticalsystem 12 includes, for example, lens groups L1 to L3. A lens barrel 12a that supports the lens groups L1 to L2 around the same is housed inthe case 141 shown in FIG. 1. Optical surfaces of lenses included in thelens groups L1 to L3 have a spherical or aspherical shape rotationallysymmetrical around the first optical axis AX1. A focusing property inthe first direction D1 and a focusing property in the second directionD2 are equal. An optical surface 12 f of the lens group L3 is exposed inan emission aperture EA at the end of a light emission side of the lensbarrel 12 a that houses the lens groups L1 to L3. Emission aperturewidth E1 in the first direction D1 of the emission aperture EA is largerthan emission aperture width E2 in the second direction D2 of theemission aperture EA (see FIG. 2B). This is because of a differencebetween longitudinal and lateral optical paths explained in detail laterand because, concerning the longitudinal first direction D1, i.e., the Ydirection, image light GL needs to be made incident on the light guidedevice 20 at relatively large light beam width and, concerning thelateral second direction D2, the image light GL needs to be madeincident on the light guide device 20 at relatively small light beamwidth.

The light guide device 20 is obtained by bonding the light guide member21 and a light transmission member 23. The light guide device 20configures a tabular optical member extending in parallel to an XY planeas a whole.

In the light guide device 20, the light guide member 21 is a prism-likemember having a trapezoidal shape in plan view. The light guide member21 has, as sides, the first reflection surface 21 a, a second reflectionsurface 21 b, the third reflection surface 21 c, and a fourth reflectionsurface 21 d. The light guide member 21 has an upper surface 21 e and alower surface 21 f adjacent to the first, second, third, and fourthreflection surfaces 21 a, 21 b, 21 c, and 21 d and opposed to eachother. The first and second reflection surfaces 21 a and 21 b extendalong the XY plane and are spaced apart by thickness t of the lightguide member 21. The third reflection surface 21 c tilts at an acuteangle α equal to or smaller than 45° with respect to the XY plane. Thefourth reflection surface 21 d tilts at an acute angle β equal to orsmaller than, for example, 45° with respect to the XY plane. The firstoptical axis AX1 passing through the third reflection surface 21 c and asecond optical axis AX2 passing through the fourth reflection surface 21d are arranged in parallel and spaced apart by a distance D. An end face21 h is provided to remove a ridge between the first reflection surface21 a and the third reflection surface 21 c. An end face 21 i is providedto remove a ridge between the first reflection surface 21 a and thefourth reflection surface 21 d. The light guide member 21 including theend faces 21 h and 21 i has an external shape of a polyhedron havingeight surfaces.

The light guide member 21 performs light guide making use of totalreflection by the first and second reflection surfaces 21 a and 21 b. Inthe light guide member 21, there is a direction in which light isreturned by reflection in the light guide and a direction in which lightis not returned by reflection in the light guide. When an image guidedby the light guide member 21 is considered, the lateral direction, i.e.,the confining direction DW2 in which the image is propagated while beingreturned by plural times of reflection in the light guide isperpendicular to the first and second reflection surfaces 21 a and 21 b(parallel to a Z axis) and, when an optical path is expanded to a lightsource side, equivalent to the second direction D2 of the liquid crystaldisplay device 32. On the other hand, the longitudinal direction, i.e.,the non-confining direction DW1 in which the image is propagated withoutbeing returned in the light guide is parallel to the first and secondreflection surfaces 21 a and 21 b and the third reflection surface 21 c(parallel to a Y axis) and, when the optical path is expanded to thelight source side as the liquid crystal display device 32. In the lightguide member 21, a main light guide direction in which a propagatedlight beam travels as a whole is parallel to a −X direction.

The light guide member 21 is formed of a resin material showing highoptical transparency in a visible range. The light guide member 21 is ablock-like member integrally molded by injection molding. The lightguide member 21 is formed by, for example, injecting a resin material ofa thermal or optical polymerization type into a molding die andthermosetting or photo-setting the resin material. The light guidemember 21 is an integral molded product in this way. However,functionally, the light guide member 21 can be considered to be dividedinto a light incident section B1, a light guide section B2, and a lightemitting section B3.

The light incident section B1 is a triangular prism-like section and hasa light incident surface IS, which is a part of the first reflectionsurface 21 a, and the third reflection surface 21 c opposed to the lightincident surface IS. The light incident surface IS is a plane on therear side or the observer side for capturing the image light GL from theimage forming device 10. The light incident surface IS is opposed to theprojection optical system 12 and extends perpendicularly to the firstoptical axis AX1. The third reflection surface 21 c has a rectangularcontour and has, in an entire area of the rectangle, a total reflectionmirror layer 25 for reflecting the image light GL, which has passedthrough the light incident surface IS, and leading the image light GLinto the light guide section B2. The total reflection mirror layer 25 isformed by applying film formation onto a slope RS of the light guidemember 21 with vapor deposition of aluminum or the like. The thirdreflection surface 21 c tilt at, for example, an acute angle α=25° to27° with respect to the first optical axis AX1 of the projection opticalsystem 12 or the XY plane. The third reflection surface 21 c bends theimage light GL, which is made incident from the light incident surfaceIS and travels in a +Z direction as a whole, to travel in a −X directioncloser to a −Z direction as a whole to surely focus the image light GLin the light guide section 32.

The light guide section B2 includes, as two planes opposed to each otherand extending in parallel to the XY plane, the first reflection surface21 a and the second reflection surface 21 b that totally reflect theimage light bent by the light incident section B1. The space between thefirst and second reflection surfaces 21 a and 21 b, i.e., the thicknesst of the light guide member 21 is set to, for example, about 9 mm. It isassumed that the first reflection surface 21 a is present on the rearside or the observer side close to the image forming device 10 and thesecond reflection surface 21 b is present on the front side or theexternal side far from the image forming device 10. In this case, thefirst reflection surface 21 a is a surface section common to the lightincident surface IS and a light emission surface OS explained later. Thefirst and second reflection surfaces 21 a and 21 b are total reflectionsurfaces that make use of a refractive index difference. A reflectioncoat such as a mirror layer is not applied to the surfaces of the firstand second reflection surfaces 21 a and 21 b. However, to prevent damageto the surfaces and a resolution fall of a video, coating of a hard coatlayer is applied. The hard coat layer is formed by forming a coatmaterial containing resin or the like on the light guide member 21through dipping or spray coating.

The image light GL reflected on the third reflection surface 21 c of thelight incident section B1 is first made incident on the first reflectionsurface 21 a and totally reflected. Subsequently, the image light GL ismade incident on the second reflection surface 21 b and totallyreflected. This operation is repeated, whereby the image light GL as awhole is guided in a main light guide direction on the depth side of thelight guide device 20, i.e., to a −X side on which the light emittingsection B3 is provided. Since a reflection coat is not applied to thefirst and second reflection surfaces 21 a and 21 b, the external lightor the natural light made incident on the second reflection surface 21 bfrom the external side passes through the light guide section B2 at hightransmittance. In other words, the light guide section B2 is asee-through type through which an external image can be seen.

The light emitting section B3 is a triangular prism-like section and hasa light emission surface OS, which is a part of the first reflectionsurface 21 a, and the fourth reflection surface 21 d opposed to thelight emission surface OS. The light emission surface OS is a plane onthe rear side for emitting the image light GL to the eye EY of theobserver. Like the light incident surface IS, the light emission surfaceOS is a part of the first reflection surface 21 a and extendsperpendicularly to the second optical axis AX2. The distance D betweenthe second optical axis AX2 passing through the light emission sectionB3 and the first optical axis AX1 passing through the light incidentsection B1 is set to, for example, 50 mm taking into account, forexample, the width of the head of the observer. The fourth reflectionsurface 21 d is a substantially rectangular flat surface for reflectingthe image light GL, which is made incident through the first and secondreflection surfaces 21 a and 21 b, and emitting the image light GL tothe outside of the light emitting section B3. A half mirror layer 28 isattached to the fourth reflection surface 21 d. The half mirror layer 28is a reflection film (i.e., a semi-transparent reflection film). Thehalf mirror layer (the semi-transparent reflection film) 28 is formed byforming a metal reflection film or a dielectric multilayer film on theslope RS of the light guide member 21. The reflectance for the imagelight GL of the half mirror layer 28 is set to 10% or more and 50% orless in an assumed incident angle range of the image light GL from theviewpoint of facilitating observation of external light GL′ bysee-through. The reflectance for the image light GL of the half mirrorlayer 28 in a specific example is set to, for example, 20% and thetransmittance for the image light GL is set to, for example, 80%.

The fourth reflection surface 21 d tilts at, for example, the acuteangle α=25° to 27° with respect to the second optical axis AX2perpendicular to the first reflection surface 21 a or the XY plane. Thefourth reflection surface 21 d partially reflects the image light GLwith the half mirror layer 28, which is made incident through the firstand second reflection surfaces 21 a and 21 b of the light guide sectionB2 and bends the image light GL to travel in the −Z direction as a wholeto cause the image light GL to pass through the light emission surfaceOS. The image light GL passed through the fourth reflection surface 21 dis made incident on the light transmission member 23 and is not used forformation of a video.

The light transmission member 23 has a refractive index same as that ofa main body of the light guide member 21 and has a first surface 23 a, asecond surface 23 b, and a third surface 23 c. The first and secondsurfaces 23 a and 23 b extend along the XY plane. The third surface 23 ctilts with respect to the XY plane and is arranged to be opposed to andparallel to the fourth reflection surface 21 d of the light guide member21. In other words, the light transmission member 23 is a member havinga wedge-like section 23 v provided between the second surface 23 b andthe third surface 23 c. Like the light guide member 21, the lighttransmission member is formed of a resin material showing high opticaltransparency in a visible range. The light transmission member 23 is ablock-like member integrally molded by injection molding. The lighttransmission member 23 is formed by, for example, injecting a resinmaterial of a thermal polymerization type into a molding die andthermosetting the resin material.

In the light transmission member 23, the first surface 23 a is arrangedon an extended plane of the first reflection surface 21 a provided inthe light guide member 21 and is present on the rear side close to theeye EY of the observer. The second surface 23 b is arranged on anextended plane of the second reflection surface 21 b provided in thelight guide member 21 and is present on the front side far from the eyeEY of the observer. The third surface 23 c is a rectangular transmissionsurface bonded to the fourth reflection surface 21 d of the light guidemember 21 by an adhesive. An angle formed by the first surface 23 a andthe third surface 23 c is equal to an angle ε formed by the secondreflection surface 21 b and the fourth reflection surface 21 d of thelight guide member 21. An angle formed by the second surface 23 b andthe third surface 23 c is equal to an angle β formed by the firstreflection surface 21 a and the third reflection surface 21 c of thelight guide member 21.

The light transmission member 23 and the light guide member 21 form, ina bonded section thereof or near the bonded section, a see-throughsection B4 in a region opposed to the eye of the observer. In the lighttransmission member 23, the wedge-like section 23 v provided between thesecond surface 23 b and the third surface 23 c, which form an acuteangle, and spreading in the −X direction is bonded to the light emittingsection B3, which is also wedge-like, to thereby form a center sectionwith respect to the X direction in the tabular see-through section B4 asa whole. Since a reflection coat such as a mirror layer is not appliedto the first and second surfaces 23 a and 23 b, like the light guidesection B2 of the light guide member 21, the first and second surfaces23 a and 23 b transmit the external light GL′ at high transmittance. Thethird surface 23 c can also transmit the external light GL′ at hightransmittance. However, since the fourth reflection surface 21 d of thelight guide member 21 includes the half mirror layer 28, the externallight GL′ passing through the third surface 23 c is reduced by, forexample, 20% in the half mirror layer 28. In other words, the observerobserves, through the half mirror layer 28, light obtained bysuperimposing the image light GL reduced to 20% and the external lightGL′ reduced to 80%.

C. Overview of an Optical Path of Image Light

FIG. 3A is a diagram for explaining an optical path in the firstdirection D1 corresponding to a longitudinal cross-section CS1 of theliquid crystal display device (the image-light forming section) 32. On alongitudinal cross-section along the first direction D1, i.e., a YZplane (a Y′Z′ plane after expansion), in image light emitted from theliquid crystal display device 32, a component indicated by an alternatelong and short dash line in the figure emitted from the upper end side(a +Y side) of a display area 32 b is represented as image light GLa anda component indicated by an alternate long and two short dashes lineemitted from the lower end side (a −Y side) of the display area 32 b isrepresented as image light GLb. In FIG. 3A, for reference, image lightGLc emitted from a position on an upper inner side and image light GLdemitted from a position on a lower inner side near the liquid crystaldisplay device 32 are shown.

The image light GLa on the upper side is converted into parallel lightbeams by the projection optical system 12, passes through the lightincident section B1, the light guide section B2, and the light emittingsection B3 of the light guide member 21 substantially along an expandedoptical axis AX′, and is made incident on the eye EY of the observer inthe parallel light beam state from an upward direction at an angle φ₁ onthe tilt. On the other hand, the image light GLb on the lower side isconverted into parallel light beams by the projection optical system 12,passes through the light incident section B1, the light guide sectionB2, and the light emitting section B3 of the light guide member 21substantially along the expanded optical axis AX′, and is made incidenton the eye EY of the observer in the parallel light beam state from adownward direction at an angle φ₂ (|φ₂|=|φ₁|) on the tilt. The angles φ₁and φ₂ are equivalent to upper and lower half angles of view and set to,for example, 6.5°.

Concerning the longitudinal direction of the first direction D1, thelight guide device 20 does not substantially affect focusing by theprojection optical system 12. The projection optical system 12 forms aninfinite image of the liquid crystal display device 32 and makes imagelight corresponding to the infinite image incident on the eye EY of theobserver.

FIG. 3B is a diagram for explaining an optical path in the seconddirection (a confining direction or a combining direction) D2corresponding to a lateral cross-section CS2 of the liquid crystaldisplay device (the image-light forming section) 32. On the lateralcross-section CS2 along the second direction (the confining direction orthe combining direction) D2, i.e., an XZ plane (an X′Z′ plane afterexpansion), in image light emitted from the liquid crystal displaydevice 32, a component emitted from a first display point P1 on theright end side (a +X side) facing the display area 32 b indicated by analternate long and short dash line in the figure is represented as imagelight GL1 and a component emitted from a second display point P2 on theleft end side (a −X side) facing the display area 32 b indicated by analternate long and two short dashes line is represented as image lightGL2. In FIG. 3B, for reference, image light GL3 emitted from a positionon a right inner side facing the display area 32 b and image light GL4emitted from a position on a left inner side facing the display area 32b near the liquid crystal display device 32 are added.

The image light GL1 from a first display point P1 on the right side isconverted into parallel light beams by the projection optical system 12,passes through the light incident section B1, the light guide sectionB2, and the light emitting section B3 of the light guide member 21substantially along the expanded optical axis and is made incident onthe eye EY of the observer in the parallel light beam state from a rightdirection at an angle θ₁ on the tilt. On the other hand, the image lightGL2 from the second display point P2 on the left side is converted intoparallel light beams by the projection optical system 12, passes throughthe light incident section B1, the light guide section B2, and the lightemitting section B3 of the light guide member 21 substantially along theexpanded optical axis AX′, and is made incident on the eye EY of theobserver in the parallel light beam state from a left direction at anangle θ₂(|θ₂|=|θ₁|) on the tilt. The angles θ₁ and θ₂ are equivalent toleft and right half angles of view and set to, for example, 10°.

Concerning the lateral direction of the second direction D2, the lightguide member 21 returns the image lights GL1 and GL2 by reflecting theimage lights. The numbers of times of reflection are different dependingon positions. Therefore, the image lights GL1 and GL2 arediscontinuously represented in the light guide member 21. As a result,concerning the lateral direction, a screen is reversed left and right asa whole. However, since the light guide member 21 is highly accuratelyprocessed as explained in detail later, an image on the right half ofthe liquid crystal display device 32 and an image on the left half ofthe liquid crystal display device 32 are continuously joined without agap. An emission angle θ₁′ of the image light GL1 on the right side andan emission angle θ₂′ of the image light GL2 on the left side are set todifferent angles taking into account the fact that the numbers of timesof reflection of the image lights GL1 and GL2 in the light guide member21 are different from each other.

Consequently, the image lights GLa, GLb, GL1, and GL2 made incident onthe eye EY of the observer are virtual images from the infinite.Concerning the longitudinal first direction D1, a video formed on theliquid crystal display device 32 is upright. Concerning the lateralsecond direction D2, a video formed on the liquid crystal display device32 is reversed.

D. Optical Path of Image Light Concerning the Lateral Direction

FIG. 4 is a sectional view for explaining a specific optical path in thelateral second direction D2 in the first display device 100A.

Image lights GL11 and GL12 from the first display point P1 on the leftside of the liquid crystal display device 32 pass through the lensgroups L1, L2, and L3 of the projection optical system 12 to beconverted into parallel light beams and are made incident on the lightincident surface IS of the light guide member 21. The image lights GL11and GL12 guided into the light guide member 21 repeat total reflectionat an equal angle on the first and second reflection surfaces 21 a and21 b and are finally emitted from the light emission surface OS asparallel light beams. Specifically, after being reflected on the thirdreflection surface 21 c of the light guide member 21 as the parallellight beams, the image lights GL11 and GL12 are made incident on thefirst reflection surface 21 a of the light guide member 21 at a firstreflection angle γ₁ and totally reflected (first total reflection).Thereafter, the image lights GL11 and GL12 are made incident on thesecond reflection surface 21 b and totally reflected while keeping thefirst reflection angle γ₁ (second total reflection) and subsequentlymade incident on the first reflection surface 21 a again and totallyreflected (third total reflection). As a result, the image lights GL11and GL12 are totally reflected on the first and second reflectionsurfaces 21 a and 21 b three times in total and made incident on thefourth reflection surface 21 d. The image lights GL11 and GL12 arereflected on the fourth reflection surface 21 d at an angle same as theangle of reflection on the third reflection surface 21 c and emittedfrom the light emission surface OS as parallel light beams at a tilt ofthe angle θ₁ with respect to the second optical axis AX2 directionperpendicular to the light emission surface OS.

Image lights GL21 and GL22 from the second display point P2 on the rightside of the liquid crystal display device 32 pass through the lensgroups L1, L2, and L3 of the projection optical system 12 to beconverted into parallel light beams and are made incident on the lightincident surface IS of the light guide member 21. The image lights GL21and GL22 guided into the light guide member 21 repeat total reflectionat an equal angle on the first and second reflection surfaces 21 a and21 b and are finally emitted from the light emission surface OS asparallel light beams. Specifically, after being reflected on the thirdreflection surface 21 c of the light guide member 21 as the parallellight beams, the image lights GL21 and GL22 are made incident on thefirst reflection surface 21 a of the light guide member 21 at a secondreflection angle γ₂ (γ₂<γ₁) and totally reflected (first totalreflection). Thereafter, the image lights GL21 and GL22 are madeincident on the second reflection surface 21 b and totally reflectedwhile keeping the second reflection angle γ₂ (second total reflection),made incident on the first reflection surface 21 a again and totallyreflected (third total reflection), made incident on the secondreflection surface 21 b again and totally reflected (fourth totalreflection), and made incident on the first reflection surface 21 aagain and totally reflected (fifth total reflection). As a result, theimage lights GL21 and GL22 are totally reflected on the first and secondreflection surfaces 21 a and 21 b five times in total and made incidenton the fourth reflection surface 21 d. The image lights GL21 and GL22are reflected on the fourth reflection surface 21 d at an angle same asthe angle of reflection on the third reflection surface 21 c and emittedfrom the light emission surface OS as parallel light beams at a tilt ofthe angle θ₂ with respect to the second optical axis AX2 directionperpendicular to the light emission surface OS.

In FIG. 4, an imaginary first surface 121 a corresponding to the firstreflection surface 21 a when the light guide member 21 is expanded andan imaginary second surface 121 b corresponding to the second reflectionsurface 21 b when the light guide member 21 is expanded are drawn. It isseen that, by expanding the light guide member 21 in this way, afterpassing through an incident equivalent surface IS′ corresponding to thelight incident surface IS, the image lights GL11 and GL12 from the firstdisplay point P1 pass through the first surface 121 a twice, passthrough the second surface 121 b once, and are emitted from the lightemission surface OS and made incident on the eye EY of the observer. Itis seen that, after passing through an incident equivalent surface IS″corresponding to the light incident surface IS, the image lights GL21and GL22 from the second display point P2 pass through the first surface121 a three times, pass through the second surface 121 b twice, and areemitted from the light emission surface OS and made incident on the eyeEY of the observer. From a different perspective, the observersuperimposedly observes the lens groups L3 at an emission end of theprojection optical system 12 present near the incident equivalentsurfaces IS′ and IS″ in different two positions.

Light beams emitted from other positions are explained. The image lightGL3 emitted from a position on the right side of the liquid crystaldisplay device 32 as one faces the same and closer to the center thanthe first display point P1 is converted into parallel light beams by theprojection optical system 12, made incident on the light guide member 21from the light incident surface IS, and, like the image lights GL11 andGL12, totally reflected on the first and second reflection surfaces 21 aand 21 b of the light guide member 21 three times in total and emittedfrom the light emission surface OS as parallel light beams at a tiltsmaller than the angle θ₁.

The image light GL4 emitted from a position on the left side of theliquid crystal display device 32 as one faces the same and closer to thecenter than the second display point P2 is converted into parallel lightbeams by the projection optical system 12, made incident on the lightguide member 21 from the light incident surface IS, and, like the imagelights GL21 and GL22, totally reflected on the first and secondreflection surfaces 21 a and 21 b of the light guide member 21 fivetimes in total and emitted from the light emission surface OS asparallel light beams at a tilt smaller than the angle θ₂.

FIG. 5A is a diagram for conceptually explaining a display surface ofthe liquid crystal display device (the image-light forming section) 32.FIG. 5B is a diagram for conceptually explaining a virtual image of theliquid crystal display device 32 visible to the observer. FIGS. 5C and5D are diagrams for explaining partial images forming the virtual image.A rectangular image forming area AD provided in the liquid crystaldisplay device 32 shown in FIG. 5A is observed as a virtual imagedisplay area AI shown in FIG. 58. On the left side of the virtual imagedisplay area AI, a first projected image IM1 equivalent to a sectionfrom the center to the right side of the image forming area AD is formed(see FIG. 5C). The first projected image IM1 is a partial image with theright side thereof cut off. On the right side of the virtual imagedisplay area AI, a projected image IM2 equivalent to a section from thecenter to the left side of the image forming area AD of the liquidcrystal display device 32 is formed as a virtual image (see FIG. 5D).The second projected image IM2 is a partial image with the left sidethereof cut off.

A first partial area A10 where only the first projected image (thevirtual image) IM1 is formed in the liquid crystal display device 32shown in FIG. 5A includes, for example, the first display point P1 atthe right end of the liquid crystal display device 32. The first partialarea A10 emits the image lights GL11 and GL12 totally reflected threetimes in total in the first light guide section B2 of the light guidemember 21. A second partial area A20 where only the second projectedimage (the virtual image) IM2 is formed in the liquid crystal displaydevice 32 includes, for example, the second display point P2 at the leftend of the liquid crystal display device 32. The second partial area A20emits the image lights GL21 and GL22 totally reflected five times intotal in the light guide section B2 of the light guide member 21. Imagelight from a band SA provided between the first and second partial areasA10 and A20 and extending longitudinally in a place closer to the centerof the image forming area AD of the liquid crystal display device 32forms an overlapping image SI shown in FIG. 5B. In other words, theimage light from the band SA of the liquid crystal display device 32changes to the first projected image IM1 formed by the image light GL3totally reflected three times in total in the light guide section B2 andthe second projected image IM2 formed by the image lights GL0 and GL4totally reflected five times in total in the light guide section B2,which are superimposed on the virtual image display area AI. If theprocessing of the light guide member 21 is precise and a light beamaccurately collimated by the projection optical system 12 is formed,concerning the overlapping image SI, it is possible to prevent a shiftand a blur due to the superimposition of the two projected images IM1and IM2.

E. Directivity of Image Light

A relation between a position in the longitudinal direction of thedisplay area 32 b of the liquid crystal display device 32 and anemission angle of image light (an angle characteristic of light beamcapturing into the projection optical system 12 or the like) isexplained with reference to FIG. 6A. In an upper half of the liquidcrystal display device 32, when an emission position (object height inthe longitudinal direction) y in the first direction D1 becomes largewhile gradually separating from the center of the liquid crystal displaydevice 32 in the longitudinal direction, an emission angle μ of imagelights FL from the display area 32 b gradually increases according tothe emission position y. As a result, although not explained in detail,an angle of the image lights FL made incident on the eye EY of theobserver also gradually increases. The same phenomenon occurs in a lowerhalf of the liquid crystal display device 32.

FIG. 6B is a graph illustrating an angle characteristic in thelongitudinal direction at the time when a virtual image is formed byimage light emitted from the liquid crystal display device 32, i.e., anangle characteristic of light beam capturing in the virtual imagedisplay apparatus 100. In the graph, the abscissa represents theemission position y in the longitudinal first direction D1 in the liquidcrystal display device and the ordinate represents the emission angle μof the effective image lights FL made incident on the eye EY in theimage light from the liquid crystal display device 32. As the emissionangle μ, a tilt angle on the upper side in the longitudinal directionwith respect to the normal of the liquid crystal display device 32,i.e., in a +y direction is plus. As it is seen from the graph, an angleof a light beam emitted from the liquid crystal display device 32 andeffectively captured into the eye EY of the observer is substantiallydifferent depending on a position of the liquid crystal display device32. More specifically, an absolute value of the emission angle μ of theeffectively-utilized image light FL tends to be larger on the peripheralside than on the center side of the display area 32 b of the liquidcrystal display device 32. In other words, as the emission position ybecomes larger and is further away from the center to the peripheralside, the emission angle from the liquid crystal display device 32 ofthe image light FL made incident on the eye EY via the light guidedevice tilts to the outer side and increases. The tilt of the emissionangle of the image light FL is the maximum at a maximum value of theemission position y, i.e., at the upper end (the peripheral section) ofthe display area 32 b. From the situation explained above, concerningfocusing in the longitudinal direction, it is considered that, byimparting directivity corresponding to the angle characteristic of lightbeam capturing shown in FIG. 6B to the image lights FL emitted from theliquid crystal display device 32, it is possible to improve opticalcoupling efficiency from the liquid crystal display device 32 to thelight guide device 20 and to the eye EY and it is possible to suppressoccurrence of luminance spots (luminance unevenness) to improveefficiency of use of illumination light. The phenomenon (the influenceof the angle characteristic of light beam capturing) becomes conspicuousas an angle of view of a virtual image increases. Therefore, to increasethe angle of view of the virtual image, it is important to impartappropriate directivity to the image lights FL emitted from the liquidcrystal display device 32.

A relation between a position in the lateral direction of the displayarea 32 b of the liquid crystal display device 32 and an emission angleof image light (an angle characteristic of light beam capturing into theprojection optical system 12 or the like) is explained with reference toFIG. 7A. In a right half (on the +X side) of the liquid crystal displaydevice 32 as one faces the same, when an emission position (objectheight in the lateral direction) x in the second direction D2 becomeslarge in a plus direction while gradually separating from the center ofthe liquid crystal display device 32 in the lateral direction, anemission angle ν of image lights FL from the display area 32 b graduallydecreases according to the emission position x. On the other hand, anangle of the image lights FL made incident on the eye EY of the observerincreases. In a left half (on the −X side) of the liquid crystal displaydevice 32 as one faces the same, when the emission position (objectheight in the lateral direction) x in the second direction D2 becomeslarge in a minus direction while gradually separating from the center ofthe liquid crystal display device 32 in the lateral direction, anabsolute value |ν| of an emission angle of the image lights FL from thedisplay area 32 b gradually decreases according to the emission positionx. As a result, although not explained in detail, an angle of the imagelights FL made incident on the eye EY of the observer also decreases.

FIG. 7B is a graph illustrating an angle characteristic in the lateraldirection at the time when a virtual image is formed by image lightemitted from the liquid crystal display device 32, i.e., an anglecharacteristic of light beam capturing in the virtual image displayapparatus 100. In the graph, the abscissa represents the emissionposition x in the lateral second direction D2 in the liquid crystaldisplay device 32 and the ordinate represents the emission angle ν ofthe effective image lights FL made incident on the eye EY in the imagelight from the liquid crystal display device 32. As the emission angleν, a tilt angle on the left side in the lateral direction with respectto the normal of the liquid crystal display device 32, i.e., in a +xdirection is plus. As it is seen from the graph, an angle of a lightbeam emitted from the liquid crystal display device 32 and effectivelycaptured into the eye EY of the observer is substantially differentdepending on a position of the liquid crystal display device 32. Morespecifically, an absolute value of the emission angle ν of theeffectively-utilized image light FL tends to be larger on the centerside than on the peripheral side of the display area 32 b of the liquidcrystal display device 32. In other words, as the emission position xbecomes smaller and is closer to the center, the emission angle from theliquid crystal display device 32 of the image light FL made incident onthe eye EY via the light guide device 20 tilts to the inner side andincreases. From the situation explained above, concerning focusing inthe lateral direction, it is considered that, by imparting directivitycorresponding to the angle characteristic of light beam capturing shownin FIG. 7B to the image lights FL emitted from the liquid crystaldisplay device 32, it is possible to improve optical coupling efficiencyfrom the liquid crystal display device 32 to the light guide device 20and to the eye EY and it is possible to suppress occurrence of luminancespots (luminance unevenness) to improve efficiency of use ofillumination light. The phenomenon (the influence of the anglecharacteristic of light beam capturing) becomes conspicuous as an angleof view of a virtual image increases. Therefore, to increase the angleof view of the virtual image, it is important to impart appropriatedirectivity to the image lights FL emitted from the liquid crystaldisplay device 32.

Concerning the center in the lateral direction of the liquid crystaldisplay device 32, an image is mainly formed by the image light GL0totally reflected five times in total in the light guide section B2. Animage is also formed to some extent by image light GL0′ totallyreflected three times in total in the light guide section B2. In thiscase, from the viewpoint of obtaining a high-luminance image, it isdesirable that an emission angle has peaks in two directions ν0 and ν0′.

FIG. 8 is a diagram for explaining the angle characteristics of lightbeam capturing shown in FIGS. 6B and 7B as a two-dimensionaldistribution. An imaginary grid is displayed on the liquid crystaldisplay device 32. The abscissa x of the imaginary grid corresponds tothe second direction D2 and the ordinate y of the grid corresponds tothe first direction D1. The directions and the sizes of arrows DA1 andDA2 extending from respective grid points indicate tilt directions andtilt amounts (i.e., azimuths and tilt angles) corresponding to peaks oflight beam capturing. The arrows DA1 of solid lines indicate light beamcapturing directions concerning the image lights GL2 and GL4 (GL0) inFIG. 7A totally reflected five times in total in the light guide sectionB2. The arrows DA2 of dotted lines indicate light beam capturingdirections concerning the image lights GL1 and GL3 (GL0′) in FIG. 7Atotally reflected three times in total in the light guide section B2. Asit is evident from the figure, the light beam capturing directions arenon-uniform in both the longitudinal direction and the lateraldirection. Image light from the band SA in the center is captured in thedirections of the two arrows DA1 and DA2. In other words, for imagelight coupled to the light guide member 21 via the projection opticalsystem 12 and propagating through the light guide member 21 to reach theeye EY or illumination light as a source of the image light, two peakdirections in which luminance is the maximum are set (specifically, thedirections of the arrows DA1 and DA2). However, if a peak of an emissionangle of the image light is present in the direction of at least one ofthe arrows DA1 and DA2, sufficient luminance can be secured in theoverlapping image SI shown in FIG. 5B and a high-quality image can beformed.

F. Control of the Directivity of Image Light in the Image Display Device

Directivity control for image light using control of the directivity ofillumination light in the image display device 11 is explained below.

FIGS. 9A to 9D are a plan view, a side view, a rear view, and apartially cut-out perspective view of the illuminating device 31 and theliquid crystal display device 32 included in the image display device11. In the image display device 11, the optical-directivity changingsection 38 is arranged between the illuminating device 31 and the liquidcrystal display device 32 and bonded to the light emission side of theilluminating device 31. The illuminating device 31 includes the lightsource 31 a, which is the light emitting section, and the backlightguide section 31 b.

In the illuminating device 31, the light source (the light emittingsection) 31 a extends along a light capturing surface IP, which is oneside of the rectangular plate-like backlight guide section 31 b. Thelight source 31 a generates light of a light amount sufficient forilluminating the liquid crystal display device (the image-light formingsection) 32 and emits the light to the backlight guide section 31 b. Asthe light source 31 a, for example, a slender fluorescent tube or alight source in which plural LED light sources are arrayed can beapplied.

The backlight guide section 31 b is a tabular member as a whole and isarranged near the back of the liquid crystal display device 32 and inparallel to the back. The backlight guide section 31 b includes a flatmember 31 e, a reflection film 31 f, and a diffusing film 31 g and has astructure in which the flat member 31 e is held between the reflectionfilm 31 f and the diffusing film 31 g. The backlight guide section 31 bmakes the illumination light SL from the light source 31 a incident onthe inside of the backlight guide section 31 b via the light capturingsurface IP, leads the incident light to be diffused by reflection, andemits the light to the liquid crystal display device 32 on the outsidevia the diffusing film 31 g and an emission surface EP to formillumination light for illuminating the entire liquid crystal displaydevice 32 from the back.

As shown in a graph of FIG. 10A, the illumination light emitted from theemission surface EP of the backlight guide section 31 b shown in FIG. 9Ais uniformalized by the backlight guide section 31 b and has a generallight distribution characteristic or light distribution. In the graph,the right half of the abscissa represents an orientation angle Econcerning the longitudinal Y direction of the illumination lightemitted from the backlight guide section 31 b. The left half of theabscissa represents an orientation angle E′ concerning the lateral Xdirection of the illumination light emitted from the backlight guidesection 31 b. The ordinate represents the luminance of the illuminationlight at the respective orientation angles. In the illumination lightemitted from the emission surface EP of the backlight guide section 31b, an optical axis AX direction (the Z direction) perpendicular to theemission surface EP is a main directivity direction in which luminanceis the highest. The illumination light has a luminance center (anintensity peak) in the optical axis AX direction (the Z direction)perpendicular to the emission surface EP. The luminance of theillumination light falls as tilt angles, i.e., the orientation angles Eand E′ increase with respect to the optical axis AX. Concerning theillumination light emitted from the backlight guide section 31 b, theoptical axis AX direction (the Z direction) perpendicular to theemission surface EP is a main directivity direction in which luminanceis the highest.

The sheet-like optical-directivity changing section 38 is bonded to theemission surface EP of the backlight guide section 31 b and integratedwith the backlight guide section 31 b. The optical-directivity changingsection 38 is a sheet of a prism array and has a function of changing alight distribution characteristic (see FIG. 10A) of the illuminationlight emitted from the emission surface EP of the backlight guidesection 31 b. The optical-directivity changing section 38 bends incidentlight at a different angle according to a position of the emissionsurface EP (i.e., a pixel position of the liquid crystal display device32). In other words, the optical-directivity changing section 38 adjuststhe light distribution characteristic, which is an angle distribution ofthe directivity of the illumination light, to thereby adjust thedirectivity of image light emitted from the liquid crystal displaydevice 32 to directivity corresponding to the angle characteristics oflight beam capturing of the virtual image display apparatus 100 shown inFIGS. 6B and 7B. The light distribution characteristic of theoptical-directivity changing section 38 is different concerning thefirst direction D1 and the second direction D2. Specifically, asexplained with reference to FIG. 6A, as an absolute value of theemission position y in the longitudinal first direction D1 increases inthe display area 32 b of the liquid crystal display device 32, a lightbeam tilting to the outer side is more effectively captured into the eyeEY of the observer passing through the projection optical system 12 andthe light guide device 20. Therefore, as explained later in detail, adistribution of the directivity of the image light emitted from theliquid crystal display device 32 is adjusted by the optical-directivitychanging section 38 to match such an angle characteristic of light beamcapturing. As explained with reference to FIG. 7A, as an absolute valueof the emission position x in the lateral second direction D2 increasesin the display area 32 b of the liquid crystal display device 32, alight beam tilting to the inner side is more effectively captured intothe eye EY of the observer passing through the projection optical system12 and the light guide device 20. Therefore, similarly, as explainedlater in detail, a distribution of the directivity of the image lightemitted from the liquid crystal display device 32 is adjusted by theoptical-directivity changing section 38 to match such an anglecharacteristic of light beam capturing. It is possible to efficientlyuse the illumination light and the image light by adjusting the lightdistribution of the illumination light using the optical-directivitychanging section 38 in this way.

The optical-directivity changing section 38 is a prism array sheethaving two-dimensionally-arrayed prism elements. An emission sidesurface of the optical-directivity changing section 38 is formed as adeflecting surface 38 a, both a longitudinal cross-section and a lateralcross-section of which are a saw-teeth like and a step like, byperiodical arrangement of the prism elements. The prism elementsincluded in the prism array sheet are arrayed at, for example, a periodlarger than that of pixels of the liquid crystal display device 32.However, the prism elements can also be arrayed at a period smaller thanthat of the pixels of the liquid crystal display device 32.

As shown in a longitudinal cross-section of FIG. 11, theoptical-directivity changing section 38 has a prism array in which prismelements are non-uniformly arrayed. A main directivity direction ofillumination lights IL is changed according to a position and tilted tothe outer side on the peripheral side. In other words, slopes of theprism elements included in the optical-directivity changing section 38face downward further in an upper side area (the +Y side) than thecenter position concerning the up down direction. A wedge angle ω of theslopes gradually increases in the prism element provided further in theupper side area. The slopes of the prism elements included in theoptical-directivity changing section 38 face upward further in a lowerside area (the −Y side) than the center position concerning the up downdirection. The wedge angle ω of the slopes gradually increases in theprism element provided further in the lower side area. The illuminationlights IL uniformly emitted from the backlight guide section 31 b aremade incident on the liquid crystal display device 32 shown in FIG. 1with a tilt angle ε given by bending in the prism elements when theillumination lights IL pass through the deflecting surface 38 a of theoptical-directivity changing section 38. The tilt angle ε is equivalentto a main direction of a light distribution of the illumination lightsIL. As illustrated in area sections AV1, AV2, and AV3 included in theupper half of the optical-directivity changing section 38, the tiltangle ε gradually increases from the center to the end on the upperside. In other words, a light distribution or a light distributioncharacteristic after passage through the optical-directivity changingsection 38 has, as indicated by a broken line in FIG. 10B, directivityin which an angle in the main direction (a direction of the luminancecenter) increases toward the outer side in a position on the upper side(the +Y side) further away from the optical axis AX (i.e., toward anarea section (a peripheral section) A21 at the upper end). On the otherhand, as illustrated in area sections AV4, AV5, and AV6 included in thelower half of the optical-directivity changing section 38, the tiltangle ε of the illumination light IL gradually increases from the centerto the end on the lower side. In other words, a light distribution or alight distribution characteristic after passage through theoptical-directivity changing section 38 has, as indicated by a brokenline in FIG. 10B, directivity in which an angle in the main direction(the direction of the luminance center) increases toward the outer sidein a position on the lower side (the −Y side) further away from theoptical axis AX (i.e., toward the area section (a peripheral section)AV6 at the lower end).

Concerning the longitudinal direction, bending, i.e., deflection of theillumination lights IL by the optical-directivity changing section 38deflects the illumination lights IL further to the outer side in theperipheral section than in the center, i.e., diffuses the illuminationlights IL to the outer side as a whole. In other words, a distributionof the tilt angle ε concerning bending in the longitudinal direction ofthe illumination lights IL by the optical-directivity changing section38 corresponds to the angle characteristic of light beam capturing shownin FIG. 6B, Consequently, the liquid crystal display device 32 isilluminated by the illumination light IL having the tilt angle εcorresponding to the emission angle μ of the image lights FL emittedfrom the liquid crystal display device 32 and effectively utilized forvirtual image formation. In other words, it is possible to substantiallymatch the emission angle μ equivalent to the luminance center of theeffective image lights FL from the liquid crystal display device 32 andthe tile angle ε equivalent to the luminance center of the illuminationlights IL from the illuminating device 31. In this way, the image lightsFL emitted from the respective positions of the liquid crystal displaydevice 32 and effectively utilized are high-luminance components.Consequently, illumination light is not wastefully used and luminancespots of a virtual image can be reduced.

As shown in a lateral cross-section of FIG. 12, the optical-directivitychanging section 38 changes a main directivity direction of theillumination lights IL according to a position and tilts the maindirectivity direction to the inner side on the center side. In otherwords, the slopes of the prism elements included in the prism array ofthe optical-directivity changing section tilt rightward further in aright side area (the +X side) than the center position concerning theleft right direction. A wedge angle ζ of the slopes gradually decreasesin the prism element provided further in a right side area. The slopesof the prism elements included in the optical-directivity changingsection 38 face leftward further in a left side area (the −X side) thanthe center position concerning the left right direction. The wedge angleζ of the slopes gradually decreases in the prism element providedfurther in a left side area. The illumination lights IL uniformlyemitted from the backlight guide section 31 b are made incident on theliquid crystal display device 32 shown in FIG. 1 with a tilt angle ηgiven by bending in the prism elements when the illumination lights ILpass through the deflecting surface 38 a of the optical-directivitychanging section 38. The tilt angle η is equivalent to a main directionof a light distribution of the illumination lights IL. As illustrated inarea sections AH1, AH2, and AH3 included in the right half of theoptical-directivity changing section 38, the tilt angle graduallydecreases from the center to the end on the right side. In other words,a light distribution or a light distribution characteristic afterpassage through the optical-directivity changing section 38 has, asindicated by a broken line in FIG. 10C, directivity in which an angle inthe main direction (a direction of the luminance center) increasestoward the left side in a position on the optical axis AX side (the −Xside) (i.e., toward the area section AH3 in the center). On the otherhand, as illustrated in area sections AH4, AH5, and AH6 included in theleft half of the optical-directivity changing section 38, the tilt angleη of the illumination light IL gradually decreases from the center tothe end on the left side. In other words, a light distribution or alight distribution characteristic after passage through theoptical-directivity changing section 38 has, as indicated by a brokenline in FIG. 10C, directivity in which an angle in the main direction(the direction of the luminance center) increases toward the outer sidein a position on optical axis AX side (the +X side) (i.e., toward thearea section AH4 in the center).

Concerning the lateral direction, bending, i.e., deflection of theillumination lights IL by the optical-directivity changing section 38deflects the illumination lights IL further to the inner side in thecenter than in the peripheral section, i.e., faces the illuminationlights IL to the opposite end or the inner side as a whole. In otherwords, a distribution of the tilt angle η concerning bending in thelateral direction of the illumination lights IL by theoptical-directivity changing section 38 corresponds to the anglecharacteristic of light beam capturing shown in FIG. 7B. Consequently,the liquid crystal display device 32 is illuminated by the illuminationlights IL having the tilt angle η corresponding to the emission angle θof the image lights FL emitted from the liquid crystal display device 32and effectively utilized for virtual image formation. In other words, itis possible to substantially match the emission angle θ equivalent tothe luminance center of the effective image lights FL from the liquidcrystal display device 32 and the tile angle η equivalent to theluminance center of the illumination lights IL from the illuminatingdevice 31. In this way, the image lights FL emitted from the respectivepositions of the liquid crystal display device and effectively utilizedare high-luminance components. Consequently, illumination light is notwastefully used and luminance spots of a virtual image can be reduced.

In the virtual image display apparatus 100 according to the embodiment,the optical-directivity changing section 38 forms a non-uniformdistribution concerning the directivity of the image lights GL emittedfrom the image display device 11. Therefore, even when an angle of alight beam emitted from the image display device 11 and effectivelycaptured into the eye EY of the observer is substantially differentdepending on a position of the image display device 11, it is possibleto form the image lights GL having directivity corresponding to such anangle characteristic of light beam capturing. It is possible to suppressoccurrence of luminance spots to improve efficiency of use ofillumination light.

In the virtual image display apparatus 100 according to the firstembodiment and embodiments explained below, adjustment of thedirectivity or the light distribution characteristic of the illuminationlights IL or the image lights GL by the optical-directivity changingsection 38 does not need to be performed concerning both the first andsecond directions D1 and D2 and can be performed concerning only one ofthe first and second directions D1 and D2.

Second Embodiment

A virtual image display apparatus according to a second embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the first embodiment. Unless specifically explained, thevirtual image display apparatus is the same as the virtual image displayapparatus 100 according to the first embodiment.

A liquid crystal display device (an image-light forming section) 132shown in FIGS. 13A and 13B incorporates an optical-directivity changingsection 138 for forming a non-uniform distribution concerning thedirectivity of image light.

The liquid crystal display device (the image-light forming section) 132is a spatial light modulating device, more specifically, alight-transmissive liquid crystal display element. The liquid crystaldisplay device 132 includes a liquid crystal panel 51 and a pair ofpolarization filters 52 a and 52 b that hold the liquid crystal panel 51therebetween. In the liquid crystal display device (the liquid crystaldisplay element) 132, the first polarization filter 52 a on an incidentside and the second polarization filter 52 b on an emission side arearranged to form a cross-Nicol across the liquid crystal panel 51. Theliquid crystal panel 51 two-dimensionally changes, in a pixel unit,according to an input signal, a polarization direction of theillumination lights IL made incident from the first polarization filter52 a side and emits modulated lights after the change to the secondpolarization filter 52 b side as image lights ML.

The liquid crystal panel 51 includes, across a liquid crystal layer 71,a first substrate 72 on the incident side and a second substrate 73 onthe emission side. The first substrate 72 on which the incident lightsLI are made incident includes a prism array 72 a extending along a YZsurface perpendicular to the optical axis AX and a main body section 72b arranged on the inner side of the prism array 72 a. The prism array 72a functions as the optical-directivity changing section 138 that adjuststhe directivity of the image lights ML. The prism array 72 a includes alarge number of very small prism elements PE two-dimensionally arrayedin a predetermined pattern corresponding to transparent pixel electrodes77, i.e., pixel portions PP.

In the liquid crystal panel 51, a transparent common electrode 75 isprovided on a surface of the first substrate 72 on the liquid crystallayer 71 side and, for example, a light distribution film 76 is formedon the common electrode 75. On the other hand, plural transparent pixelelectrodes 77 arranged in a matrix shape and a thin film transistor (notshown) electrically connected to the transparent pixel electrodes 77 areprovided on a surface of the second substrate 73 on the liquid crystallayer 71 side. For example, a light distribution film 78 is formed onthe transparent pixel electrodes 77 and the thin film transistor. Aninner section (i.e., the main body section 72 b) of the first substrate72, the second substrate 73, the liquid crystal layer 71 held betweenthe first substrate 72 and the second substrate 73, and electrodes 75and 77 are sections that function as an optical active element, i.e., aliquid crystal device 80 for modulating a polarization state of theincident lights IL according to an input signal. Each of the pixelportions PP included in the liquid crystal display 80 includes onetransparent pixel electrode 77, a part of the common electrode 75, apart of the light distribution films 76 and 78, and a part of the liquidcrystal layer 71. The illumination lights IL can be made incident on thepixel portions PP with a tilt angle of the illumination lights ILadjusted by elements of the prism array 72 a provided on the firstsubstrate 72 on the incident side. A black matrix 79 of a lattice shapeis provided between the first substrate 72 and the common electrode 75to distinguish the pixel portions PP.

The prism array 72 a, which is the optical-directivity changing section138, is incorporated instead of the optical-directivity changing section38 in the first embodiment shown in FIG. 9A and the like. As in the caseof the first embodiment, the prism array 72 a bends, concerning thelongitudinal direction, illumination light made incident from thebacklight guide section 31 b to the outer side and bends, concerning thelateral direction, the illumination light made incident from thebacklight guide section 31 b to the inner side.

Specifically, as shown in a longitudinal cross-section of FIG. 13A, theprism array 72 a includes the prism elements PE, the wedge angle ω ofwhich gradually increases toward the upper side (the +Y side) in asection further on the upper side than the center. The illuminationlights IL uniformly emitted from the backlight guide section 31 b shownin FIG. 2A are made incident on the liquid crystal display device 80with the upward tilt angle δ given when the illumination lights IL passthrough prism elements PE. Although not shown in the figure, the prismarray 72 a includes the prism elements PE, the wedge angle ω of whichgradually increases toward the lower side (the −Y side) in a sectionfurther on the lower side than the center. The illumination lights ILuniformly emitted from the backlight guide section 31 b are madeincident on the liquid crystal display device 80 with the downward tiltangle ε given when the illumination lights IL pass through refractingsurfaces or deflecting surfaces of the prism elements PE. As in the caseof the first embodiment, a distribution of the tilt angle ε correspondsto the angle characteristic of light beam capturing shown in FIG. 6B.Consequently, the liquid crystal display device 132 is illuminated bythe illumination lights IL having the tilt angle ε corresponding to theemission angle μ of the effective image lights FL extracted from theliquid crystal display device 132 and effectively utilized for virtualimage formation. Therefore, illumination light is not wastefully usedand luminance spots of a virtual image can be reduced.

As shown in a lateral cross-section of FIG. 13B, the prism array 72 aincludes the prism elements PE, the wedge angle ζ of which graduallyincreases toward the left side (the −X side) in a section further on theright side than the center. The illumination lights IL uniformly emittedfrom the backlight guide section 31 b shown in FIG. 2A are made incidenton the liquid crystal display device 80 with the leftward tilt angle ηgiven when the illumination lights IL pass through the prism elementsPE. Although not shown in the figure, the prism array 72 a includes theprism elements PE, the wedge angle ζ of which gradually increases towardthe right side (the +X side) in a section further on the left side thanthe center. The illumination lights IL uniformly emitted from thebacklight guide section 31 b are made incident on the liquid crystaldisplay device 80 with the downward tilt angle η given when theillumination lights IL pass through the refracting surfaces or thedeflecting surfaces of the prism elements PE. As in the case of thefirst embodiment, a distribution of the tilt angle η corresponds to theangle characteristic of light beam capturing shown in FIG. 7B.Consequently, the liquid crystal display device 132 is illuminated bythe illumination lights IL having the tilt angle η corresponding to theemission angle θ of the effective image lights FL extracted from theliquid crystal display device 132 and effectively utilized for virtualimage formation. Therefore, illumination light is not wastefully usedand luminance spots of a virtual image can be reduced.

As explained above, in the case of this embodiment, an image displaydevice includes the liquid crystal display device 132 excluding theoptical-directivity changing section 138 and the illuminating device 31.

FIGS. 14A and 14B are a modification of the liquid crystal displaydevice 132 shown in FIGS. 13A and 13B. In this case, a prism array 73 ais embedded in the second substrate 73 on the emission side.Specifically, the second substrate 73 includes a prism array 73 aextending along the YZ plane perpendicular to the optical axis AX and amain body section 73 b arranged on the inner side of the prism array 73a. The prism array 73 a includes a large number of prism elements PEtwo-dimensionally arrayed in a predetermined pattern corresponding tothe transparent pixel electrodes 77, i.e., the pixel portions PP. Asshown in FIG. 14A, the prism array 73 a includes the prism elements PE,the wedge angle ω of which gradually increases toward the upper side(the +Y side) in a section further on the upper side than the center ofthe longitudinal cross-section. The image lights ML emitted from theliquid crystal device 80 are emitted from the liquid crystal displaydevice 132 with the upward tilt angle ε given when the image lights MLpass through the refracting surfaces or the deflecting surfaces of theprism elements PE. As shown in FIG. 14B, the prism array 73 a includesthe prism elements PE, the wedge angle ζ of which gradually increasestoward the left side (the −X side) in a section further on the rightside than the center of the lateral cross-section. The image lights MLemitted from the liquid crystal device 80 are emitted from the liquidcrystal display device 132 with the upward tilt angle η given when theimage lights ML pass through the refracting surfaces or the deflectingsurfaces of the prism elements PE.

In the virtual image display apparatus 100 according to this embodiment,an emitting direction of the image lights ML can be adjusted in a pixelunit of the liquid crystal display device 132. Consequently, even whenthe tilt of the effective image lights FL (image lights ML) emitted fromthe liquid crystal display device 132 and effectively captured into theeye EY of the observer has deviation to correspond to an area on ascreen, it is possible to form the image lights ML having directivitycorresponding to the deviation. It is possible to suppress occurrence ofluminance spots to improve efficiency of use of illumination light.

The prism array 73 a can also be externally attached to the liquidcrystal display device 132, for example, bonded to the outer sides ofthe first and second substrates 72 and 73.

Third Embodiment

A virtual image display apparatus according to a third embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the first or second embodiment. Unless specificallyexplained, the virtual image display apparatus is the same as thevirtual image display apparatus 100 according to the first embodiment.

A liquid crystal display device (an image-light forming section) 232shown in FIGS. 15A and 15B is a light-transmissive liquid crystaldisplay element incorporating an optical-directivity changing section238 for forming a non-uniform distribution concerning the directivity ofimage light. In the case of this embodiment, an image display deviceincludes the liquid crystal display device (the image-light formingsection) 232 excluding the optical-directivity changing section 238 andthe illuminating device 31 not shown in the figure.

In the liquid crystal panel 51 of the liquid crystal display device 232,the first substrate 72 on the light incident side includes a micro lensarray 272 a extending along the YZ plane perpendicular to the opticalaxis AX and a main body section 72 b arranged on the inner side of themicro lens array 272 a. The micro lens array 272 a functions as theoptical-directivity changing section 238 that adjusts the directivity ofthe image lights ML. The micro lens array 272 a includes a large numberof lens elements LE two-dimensionally arrayed in a predetermined patterncorresponding to the transparent pixel electrodes 77, i.e., the pixelportions PP. As shown in FIG. 15A, a pitch Pm in the Y direction of themicro lens array 272 a is slightly larger than a pitch Pc in the Ydirection of the pixel portions PP. Therefore, concerning the Ydirection or the longitudinal direction, the optical axes or the centersof the lens elements LE are gradually decentered from the centers of thepixel portions PP. In other words, in the micro lens array 272 a, thedecenter gradually increases toward the upper side (the 4-Y side) in thesection further on the upper side than the center. The decentergradually increases toward the lower side (the −Y side) in a sectionfurther on the lower side than the center as well. As shown in FIG. 15B,a pitch Pm′ in the x direction of the micro lens array 272 a is slightlylarger than a pitch Pc′ in the Y direction of the pixel portions PP.Therefore, concerning the X direction or the lateral direction, theoptical axes or the centers of the lens elements LE are graduallydecentered from the centers of the pixel portions PP. In other words, inthe micro lens array 272 a, the decenter gradually increases toward theleft side (the −X side) in the section further on the right side thanthe center. The decenter gradually increases toward the right side (the+X side) in a section further on the left side than the center as well.

The illumination lights IL uniformly emitted from the backlight guidesection 31 b shown in FIG. 2A are made incident on the liquid crystaldevice 80 with the upward or downward tilt angle ε given and with therightward or leftward tilt angle η given such that the illuminationlights IL are diffused rather than being simply focused when theillumination lights IL pass through the refracting surface or thedeflecting surface of the micro lens array 272 a. As in the case of thefirst embodiment, a distribution of the tilt angles ε and η correspondsto the angle characteristics of light beam capturing shown in FIG. 6Band FIG. 7B. Consequently, the liquid crystal display device 232 isilluminated by the illumination lights IL having the tilt angles ε and ηcorresponding to the emission angles μ and θ of the image light FLextracted from the liquid crystal display device 232 and effectivelyutilized for virtual image formation. Therefore, illumination light isnot wastefully used and luminance spots of a virtual image can bereduced. When the micro lens array 272 a is used, light beams blocked bythe black matrix 79 can be reduced by focusing the illumination lightsIL and further improvement of light use efficiency can be expected.

FIGS. 16A and 16B are a modification of the liquid crystal displaydevice 232 shown in FIGS. 15A and 15B. In this case, a micro lens array273 a is embedded in a second substrate 273 on the emission side.Specifically, the second substrate 273 includes a micro lens array 273 aextending along the YZ plane perpendicular to the optical axis AX and amain body section 73 b arranged on the inner side of the micro lensarray 273 a. The micro lens array 273 a includes the large number oflens elements LE two-dimensionally arrayed in a predetermined patterncorresponding to the transparent pixel electrodes 77, i.e., the pixelportions PP. As shown in a longitudinal cross-section of FIG. 16A, themicro lens array 273 a has a structure in which the decenter graduallyincreases toward the upper side (the +Y side) in a section further onthe upper side than the center. The image lights ML emitted from theliquid crystal device 80 are emitted from the liquid crystal displaydevice 232 with the upward tilt angle ε given when the image lights MLpass through the refracting surfaces or the deflecting surfaces of thelens elements LE. Although not shown in the figure, the decentergradually increases toward the lower side (the −Y side) in a sectionfurther on the lower side than the center. As shown in a lateralcross-section of FIG. 16B, the micro lens array 273 a has a structure inwhich the decenter gradually increases toward the left side (the −Xside) in a section further on the right side than the center and thedecenter gradually increases toward the right side (the +X side) in asection further on the left side than the center.

In the liquid crystal display device 232 shown in FIGS. 16A and 16B, themicro lens array 272 a as the optical-directivity changing section 238can be embedded in the first substrate 72 on the incident side as well.

In the virtual image display apparatus 100 according to this embodiment,an emitting direction of the image lights ML can be adjusted in a pixelunit of the liquid crystal display device 232. Consequently, even whenthe tilt of the effective image lights FL (image lights ML) emitted fromthe liquid crystal display device 232 and effectively captured into theeye EY of the observer has deviation to correspond to an area on ascreen, it is possible to form the image lights ML having directivitycorresponding to the deviation. It is possible to suppress occurrence ofluminance spots to improve efficiency of use of illumination light.

The prism array 73 a can also be externally attached to the liquidcrystal display device 232, for example, bonded to the outer sides ofthe first and second substrates 72 and 73.

Fourth Embodiment

A virtual image display apparatus according to a fourth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the first embodiment. Unless specifically explained, thevirtual image display apparatus is the same as the virtual image displayapparatus 100 according to the first embodiment.

As shown in FIG. 17, the image display device 11 includes anilluminating device 431, which is a surface-light-source-like lightemitting section, instead of the light source 31 a shown in FIG. 2A. Thebacklight guide section 31 b is unnecessary. In other words, thesurface-light-source-like light emitting section is a planar lightsource that spreads two-dimensionally in itself. The optical-directivitychanging section 38 is arranged between the illuminating device 431 andthe liquid crystal display device (the image-light forming section) 32.More specifically, the optical-directivity changing section 38 is bondedon the emission surface EP on the liquid crystal display device (theimage-light forming section) 32 side of the illuminating device 431 andintegrated with the emission surface EP. As in the case of the firstembodiment, the optical-directivity changing section 38 can form adistribution of desired directivity in the illumination lights SL and,as a result, can give a distribution of desired directivity to the imagelights ML as well. In the surface-emission illuminating device (thesurface-light-source-like light emitting section) 431, for example,light emitting elements such as organic EL elements or LEDs aretwo-dimensionally arrayed uniformly.

Fifth Embodiment

A virtual image display apparatus according to a fifth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the first to fourth embodiments. Unless specificallyexplained, the virtual image display apparatus is the same as thevirtual image display apparatus 100 according to the first embodiment.

FIG. 18 is a diagram for explaining the image display device 11incorporated in the virtual image display apparatus according to thefifth embodiment. In the case of the virtual image display apparatusaccording to the fifth embodiment, in the image display device 11 shownin FIG. 2A, a self-emitting organic EL display device (EL displayelement) 532 is used instead of the optical-modulation liquid crystaldisplay devices (image-light forming sections) 32 and 232 or the like.In this case, the illuminating device 31 is unnecessary. Desireddirectivity is given to an emitting direction of the image light ML bythe prism array 73 a embedded in the organic EL display device (ELdisplay element) 532.

The organic EL display device 532 shown in the figure is explained usingan enlarged longitudinal cross-section of one pixel portion PP and theperiphery of the pixel portion PP. The structure of the organic ELdisplay device 532 is briefly explained. The organic EL display device532 is formed on a Si substrate 61 and has a structure in which aninsulating layer 62, a light emitting layer 63, a light-transmissivecathode layer 65, a bonding layer 66, a sealing layer 67, and a lighttransmission substrate 68 are sequentially laminated on the Si substrate61. On the Si substrate 61, for example, a driving circuit for theorganic EL display device 532 is formed. An electrode area 61 aextending from the driving circuit is connected to an anode 64 piercingthrough the insulating layer 62 and extending to the light emittinglayer 63. The light emitting layer 63 includes a light emitting area 63a provided between the anode 64 and the light-transmissive cathode layer65. On the light-transmissive cathode layer 65, the light transmissionsubstrate 68 is bonded across the bonding layer 66 and the sealing layer67. In the bonding layer 66 provided between the light-transmissivecathode layer and the sealing layer 67, the prism array 73 a is formedas the optical-directivity changing section 538 to be embedded in thebonding layer 66.

The image light ML from the pixel portions PP of the organic EL displaydevice 532 shown in the figure is given, for example, the upward tiltangle ε when the image light ML passes through refracting surfaces ordeflecting surfaces of the prism array 73 a. In the entire organic ELdisplay device 532, as in the case of the second and third embodiments,for example, the image light ML having directivity in a two-dimensionaldistribution corresponding to light beam capturing peaks indicated bythe arrows DA1 and DA2 in FIG. 8 can be formed.

The prism array 73 a as the optical-directivity changing section 538includes the plural prism elements PE, tilt angles of which areadjusted, in order to adjust the directivity of the image light ML. Inan example shown in the figure, the prism array 73 a is formed to beseparated in a pixel unit of the organic EL display device 532. However,the prism array 73 a can also be formed over the entire display surfaceof the organic EL display device 532. In the example shown in thefigure, the plural prism elements PE are provided for one pixel.However, the size of a single prism element PE can be increased to coverone pixel.

In the virtual image display apparatus 100 according to this embodiment,an emitting direction of the image light ML can be adjusted in a pixelunit of the organic EL display device 532. Consequently, even when thetilt of effective image light FL (image light ML) emitted from theorganic EL display device 532 and effectively captured into the eye EYof the observer has local deviation to correspond to an area on ascreen, it is possible to form the image light ML having directivitycorresponding to the deviation. It is possible to suppress occurrence ofluminance spots to improve efficiency of use of illumination light.

The prism array 73 a can be replaced with a lens array having a functionof causing a light beam to converge. The prism array 73 a is not alwaysarranged in the organic EL display device 532 and can be arranged on alight emission surface of the organic EL display device 532.

In the above explanation, the organic EL display device 532 is used as aself-emitting display device incorporated in the image display device11. However, the self-emitting display device is not limited to theorganic EL display device 532 and can be a self-emitting display deviceof another type different from organic EL.

Sixth Embodiment

A virtual image display apparatus according to a sixth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the first to fifth embodiments. Unless specificallyexplained, the virtual image display apparatus is the same as thevirtual image display apparatus 100 according to the first to fifthembodiments.

FIG. 19A is a diagram for explaining a light guide member 621 obtainedby modifying the light guide member 21 shown in FIG. 2A and the like. Inthe above explanation, the image light propagating through the lightguide member 21 is totally reflected at only the two reflection anglesγ1 and γ2 with respect to the first and second reflection surfaces 21 aand 21 b. However, as in the light guide member 621 according to themodification shown in FIG. 19A, it is also possible to allow imagelights GL31, GL32, and GL33 of three components to be respectivelytotally reflected at reflection angles γ1, γ2, and γ3 (γ1>γ2>γ3). Inthis case, the image lights GL emitted from the liquid crystal displaydevice 32 are propagated in three modes, combined in the position of theeye EY of the observer, and recognized as a virtual image. In this case,as shown in FIG. 19B, a projected image IM21 totally reflected, forexample, three times in total is formed on the left side of an effectivedisplay area A0, a projected image IM22 totally reflected, for example,five times in total is formed close to the center of the effectivedisplay area A0, and a projected image IM23 totally reflected, forexample, seven times in total is formed on the right side of theeffective display area A0.

Seventh Embodiment

A virtual image display apparatus according to a seventh embodiment isexplained below. The virtual image display apparatus according to thisembodiment is modification of the virtual image display apparatus 100according to the first to sixth embodiments. Unless specificallyexplained, the virtual image display apparatus is the same as thevirtual image display apparatus 100 according to the first to sixthembodiments.

The virtual image display apparatus 100 shown in FIGS. 20A to 20Cincludes the image forming device 10 and the light guide device 720 as aset. The light guide device 720 includes a light guide member 721 as apart thereof. The light guide member 721 includes a light guide bodysection 20 a and an angle converting section 723, which is an imageextracting section. FIG. 20A corresponds to an A-A cross-section of thelight guide member 721 shown in FIG. 20B.

The overall external view of the light guide member 721 is formed by thelight guide body section 20 a, which is a flat plate extending inparallel to the YZ plane in the figure. The light guide member 721 hasas sides, the first reflection surface 21 a, the second reflectionsurface 21 b, and the third reflection surface 21 c. The light guidemember 721 has an upper surface 21 e and a lower surface 21 f adjacentto the first to third reflection surfaces 21 a to 21 c and opposed toeach other. The light guide member 721 includes the angle convertingsection 723 including a large number of very small mirrors embedded inthe light guide body section 20 a at an end in a longitudinal directionof the light guide member 721. The light guide member 721 includes theprism section PS formed to expand the light guide body section 20 a atthe other end in the longitudinal direction and the third reflectionsurface 21 c attached to the prism section PS. The light guide member721 is an integral component. However, as in the case of the firstembodiment, the light guide member 721 can be considered to be dividedinto the light incident section B1, the light guide section B2, and thelight emitting section B3. The light incident section 31 is a sectionincluding the third reflection surface 21 c and the light incidentsurface IS explained later. The light guide section B2 is a sectionincluding the first and second reflection surfaces 21 a and 21 b. Thelight emitting section B3 is a section including the angle convertingsection 723 and the light emission surface OS explained later.

The light guide body section 20 a is formed of a light-transmissiveresin material or the like. The light guide body section 20 a includes,on a plane on the rear side or the observer side parallel to the XYplane and opposed to the image forming device 10, the light incidentsurface IS that captures image light from the image forming device 10and the light emission surface OS that emits the image light to the eyeEY of the observer. The light guide body section 20 a includes, as aside of the prism section PS, a rectangular slope RS other than thelight incident surface IS. The mirror layer 25 is formed on the slope RSto cover the slope RS. The mirror layer 25 functions as, by cooperatingwith the slope RS, the third reflection surface 21 c, which is anincident light bending section arranged to be tilted with respect to thelight incident surface IS. The third reflection surface 21 c bends imagelight, which is made incident from the light incident surface IS andtravels in the +Z direction as a whole, to travel in the −X directiondeviating to the −Z direction as a whole to surely focus the image lightin the light guide body section 20 a. In the light guide body section 20a, the angle converting section 723, which is a micro structure, isformed along a plane on the rear side of the light emission surface OS.The light guide body section 20 a extends from the third reflectionsurface 21 c on the entrance side to the angle converting section 723 onthe depth side and leads the image light, which is made incident on theinside of the light guide body section 20 a via the prism section PS, tothe angle converting section 723.

The first and second reflection surfaces 21 a and 21 b of the lightguide member 721 are principal planes of the tabular light guide bodysection 20 a and function as two planes opposed to each other andextending in parallel to the XY plane to totally reflect image lightbent by the prism section PS. Image light reflected on the thirdreflection surface 21 c is first made incident on the first reflectionsurface 21 a and totally reflected. Subsequently, the image light ismade incident on the second reflection surface 21 b and totallyreflected. This operation is repeated, whereby the image light is guidedto the depth side of the light guide device 720, i.e., the −X side onwhich the angle converting section 723 is provided.

The angle converting section 723 arranged to be opposed to the lightemission surface OS of the light guide body section 20 a is formed alongan extended plane of the second reflection surface 21 b and near theextended plane on the depth side (the −X side) of the light guide member721. The angle converting section 723 reflects image light, which ismade incident through the light guide member 721 and the first andsecond reflection surfaces 21 a and 21 b, at a predetermined angle andbends the image light to the light emission surface OS side. In otherwords, the angle converting section 723 converts the angle of the imagelight. It is assumed that image light made incident on the angleconverting section 723 first is a target to be extracted as virtualimage light. A detailed structure of the angle converting section 723 isexplained later with reference to FIG. 21A and the like.

A refractive index n of a transparent resin material used for the lightguide body section 20 a is equal to or higher than 1.5. Since thetransparent resin material having the relatively high refractive indexis used for the light guide member 721, it is easy to guide image lighton the inside of the light guide member 721 and it is possible to set anangle of view of the image light on the inside of the light guide member721 relatively small.

Image light emitted from the image forming device 10 and made incidenton the light guide member 721 from the light incident surface IS isuniformly reflected and bent on the third reflection surface 21 c. Theimage light is repeatedly totally reflected on the first and secondreflection surfaces 21 a and 21 b of the light guide member 721 andtravels while having a fixed spread substantially along the optical axisAX. Further, the image light is bent at a proper angle in the angleconverting section 723 to be changed to an extractable state. Finally,the image light is emitted to the outside from the light emissionsurface OS. The image light emitted to the outside from the lightemission surface OS is made incident on the eye EY of the observer asvirtual image light. The virtual image light is focused on the retina ofthe observer, whereby the observer can recognize image light such asvideo light by a virtual image.

An optical path of image light in the light guide member 721 isexplained below. The light guide device 720 in the seventh embodimentfunctions in the same manner as the light guide device 20 shown in FIG.1A concerning the longitudinal first direction D1 (the Y direction). Onthe other hand, the light guide device 720 guides image light in a largenumber of propagation modes concerning the lateral second direction D2(the X direction). The light guide device 720 is different from thelight guide device 20 shown in FIG. 2A that guides image light in twopropagation modes.

As shown in FIG. 20A, in image light emitted from the liquid crystaldisplay device (the image-light forming section) 32 of the image displaydevice 11, a component indicated by a dotted line emitted from thecenter of the emission surface 32 a is represented as image light GL01,a component indicated by an alternate long and short dash line emittedfrom the right side on the paper surface (the +X side) of the emissionsurface 32 a is represented as image light GL02, and a componentindicated by an alternate long and two short dashes line emitted fromthe left side on the paper surface (the −X side) of the emission surface32 a is represented as GL03.

After being made incident from the light incident surface Is of thelight guide member 721, the main components of the image lights GL01,GL02, and GL03 passed through the projection optical system 12 repeattotal reflection at angles different from one another on the first andsecond reflection surfaces 21 a and 21 b. Specifically, among the imagelights GL01, GL02, and GL03, the image light GL01 emitted from thecenter of the emission surface 32 a of the liquid crystal display device(the image-light forming section) 32 is, after being made incident onthe light incident surface IS as parallel light beams and reflected onthe third reflection surface 21 c, made incident on the first reflectionsurface 21 a of the light guide member 721 at a standard reflectionangle and totally reflected. Thereafter, the image light GL01 repeatstotal reflection on the first and second reflection surfaces 21 a and 21b while keeping the standard reflection angle γ₀. The image light GL01is totally reflected N times (N is a natural number) on the first andsecond reflection surface 21 a and 21 b and made incident on a centersection 23 k of the angle converting section 723. The image light GL01is reflected in the center section 23 k at a predetermined angle andemitted from the light emission surface OS as parallel light beams inthe optical axis AX direction perpendicular to the XY plane includingthe light emission surface OS. The image light GL02 emitted from one endside (the +X side) of the emission surface 32 a of the liquid crystaldisplay device 32 is, after being made incident on the light incidentsurface IS as parallel light beams after passage through the projectionoptical system 12 and reflected on the third reflection surface 21 c,made incident on the first reflection surface 21 a of the light guidemember 721 at a maximum reflection angle γ⁺ and totally reflected. Theimage light GL02 is totally reflected, for example, N−M times (M is anatural number) on the first and second reflection surfaces 21 a and 21b, reflected in a peripheral section 23 h at the end of the depth side(the −X side) of the angle converting section 723 at a predeterminedangle and emitted from the light emission surface OS as parallel lightbeams in a predetermined angle direction. An emission angle in theemission is set to an angle for returning the image light GL02 to thethird reflection surface 21 c side and is an acute angle with respect toa +X axis. The image light GL03 emitted from the other end side (the −Xside) of the emission surface 32 a of the liquid crystal display deviceis, after being made incident on the light incident surface IS asparallel light beams after passage through the projection optical system12 and reflected on the third reflection surface 21 c, made incident onthe first reflection surface 21 a of the light guide member 721 at aminimum reflection angle and totally reflected. The image light GL03 istotally reflected, for example, N+M times on the first and secondreflection surfaces 21 a and 21 b, reflected in a peripheral section 23m at the end of the entrance side (the +X side) of the angle convertingsection 723 at a predetermined angle and emitted from the light emissionsurface OS as parallel light beams in a predetermined angle direction.An emission angle in the emission is set to an angle for separating theimage light GL03 from the third reflection surface 21 c side and is anobtuse angle with respect to the +X axis.

When a value of the refractive index n of the transparent resin materialused for the light guide member 721 is set to n=1.5 as an example, avalue of a critical angle γc of the transparent resin material isγc≡41.8°. When the value of the refractive index n is set to n=1.6, thevalue of the critical angle γc is γc≡38.7°. The minimum reflection angleγ⁻ among the reflection angles γ₀, γ₊, and γ⁻ of the image lights GL01,GL02, and GL03 is set to a value larger than the critical angle γc,whereby a total reflection condition in the light guide member 721 canbe satisfied concerning necessary image light.

The structure of the angle converting section 723 and bending of anoptical path of image light by the angle converting section 723 areexplained in detail below with reference to FIG. 21A and the like.

First, the structure of the angle converting section 723 is explained.The angle converting section 723 includes a large number of linearreflection units 2 c arrayed in a stripe shape. Specifically, the angleconverting section 723 is configured by arraying the slender reflectionunits 2 c, which extend in the Y direction, along the main light guidedirection in which the light guide member 721 extends, i.e., the −Xdirection at predetermined pitches PT. Each of the reflection units 2 cincludes, as a set, a first reflection surface 2 a, which is onereflection surface section, arranged on the depth side, i.e., an opticalpath downstream side and a second reflection surface 2 b, which isanother reflection surface section, arranged on the entrance side, i.e.,an optical path upstream side. At least the second reflection surface 2b is a partial reflection surface that can transmit a part of light andenables the observer to observe an external image seeing through thesecond reflection surface 2 b. The reflection unit 2 c is formed in a Vshape or a wedge shape in XZ sectional view by the first and secondreflection surfaces 2 a and 2 b adjacent to each other. Morespecifically, the first and second reflection surfaces 2 a and 2 blinearly extend in a longitudinal direction set in the Y direction,i.e., a direction extending perpendicularly to a ±X direction, which isparallel to the second reflection surface 21 b and is an array directionin which the reflection units 2 c are arrayed. Further, the first andsecond reflection surfaces 2 a and 2 b tilt, with the longitudinaldirection as an axis, respectively at different angles with respect tothe second reflection surface 21 b (angles different with respect to theXY plane). As a result, the first reflection surfaces 2 a areperiodically repeatedly arrayed and extend in parallel to one another.The second reflection surfaces 2 b are also periodically repeatedlyarrayed and extend in parallel to one another. In a specific exampleshown in FIGS. 21A to 21C and the like, the first reflection surfaces 2a extend along a direction substantially perpendicular to the secondreflection surface 21 b (the Z direction). The second reflectionsurfaces 2 b extend in a direction at a predetermined angle (a relativeangle) δ in the clockwise direction with respect to the first reflectionsurfaces 2 a corresponding to the second reflection surfaces 2 b. Therelative angle δ is set to, for example, 54.7° in the specific example.

In the specific example shown in FIG. 21A and the like, the firstreflection surfaces 2 a are substantially perpendicular to the secondreflection surface 21 b. However, the direction of the first reflectionsurfaces 2 a is adjusted as appropriate according to the specificationsof the light guide device 720 and can be set, with respect to the secondreflection surface 21 b, at any tilt angle in a range of, for example,80° to 100° counterclockwise with reference to the +X direction. Thedirection of the second reflection surfaces 2 b can be set at any tiltangle in a range of, for example, 30° to 40° counterclockwise withreference to the +X direction. As a result, the second reflectionsurfaces 2 b have any relative angle in a range of 40° to 70° withrespect to the first reflection surface 2 a.

The reflection unit 2 c including a pair of the reflection surfaces 2 aand 2 b is formed by, for example, applying film formation such asaluminum vapor deposition to one slope of a V groove of a base.Thereafter, the reflection unit 2 c is embedded in the light guidedevice 720 by filling resin.

Bending of optical paths of image lights by the angle converting section723 is explained in detail below. Among the image lights, the imagelight GL02 and the image light GL03 made incident on both end sides ofthe angle converting section 723 are explained below. Since otheroptical paths are the same as those of the image light GL02 and theimage light GL03, illustration and the like of the optical paths areomitted.

As shown in FIGS. 21A and 21B, the image light GL02 guided at thereflection angle γ₊ of largest total reflection angle among the imagelights is made incident on one or more reflection units 2 c arranged inthe peripheral section 23 h on the −X side most distant from the lightincident surface IS (see FIG. 20A) in the angle converting section 723.In the reflection unit 2 c, the image light GL02 is first reflected onthe first reflection surface 2 a on the depth side, i.e., the −X sideand subsequently reflected on the second reflection surface 2 b on theentrance side, i.e., the +X side. The image light GL02 passed throughthe reflection unit 2 c is emitted from the light emission surface OSshown in FIG. 20A and the like without passing through the otherreflection units 2 c. In other words, the image light GL02 is bent at adesired angle by passing through the angle converting section 723 onlyonce and is extracted to the observer side.

As shown in FIGS. 21A and 21C, the image light GL03 guided at thesmallest reflection angle γ⁻ of the total reflection angle is madeincident on one or more reflection units 2 c arranged in the peripheralsection 23 m on the +X side closest to the light incident surface IS(see FIG. 20A) in the angle converting section 723. In the reflectionunit 2 c, the image light GL03, similarly to the image light GL02, isfirst reflected on the first reflection surface 2 a on the depth side,i.e., the −X side and subsequently reflected on the second reflectionsurface 2 b on the entrance side, i.e., the +X side. The image lightGL03 passed through the reflection unit 2 c is bent at a desired angleby passing through the angle converting section 723 only once withoutpassing through the other reflection units 2 c and is extracted to theobserver side.

In the case of the reflection in the two stages on the first and secondreflection surfaces 2 a and 2 b explained above, as shown in FIGS. 21Band 21C, all bending angles φ, which are angles formed by directionsduring incidence and directions during emission of image lights areφ=2(R−δ) (R: right angle). In other words, the bending angles φ arefixed irrespective of values of incident angles on the angle convertingsection 723, i.e., the reflection angles γ₀, γ₊, γ⁻, and the like, whichare total reflection angles of the image lights. Consequently, even whena component having a relatively large total reflection angle of imagelights is made incident on the peripheral section 23 h side on the −Xside in the angle converting section 723 and a component having arelatively small total reflection angle is made incident on theperipheral section 23 m side on the +x side in the angle convertingsection 723 as explained above, it is possible to efficiently extractthe image lights in an angle state in which the image lights arecollected in the eye EY of the observer as a whole. Since the imagelights are extracted in such an angle relation, the light guide member721 can cause the image lights to pass only once without causing theimage lights to pass plural times in the angle converting section 723and makes it possible to extract the image lights as virtual imagelights with a small loss.

In an optical design of the shape and the refractive index of the lightguide member 721, the shape of the reflection unit 2 c included in theangle converting section 723, and the like, angles and the like at whichthe image lights GL02 and GL03 and the like are guided are adjusted asappropriate. This makes it possible to make image lights emitted fromthe light emission surface OS incident on the eye EY of the observer asvirtual image lights with symmetry of the image lights kept as a wholewith the basic image light GL01, i.e., the optical axis AX as thecenter. An angle θ₁₂ (θ₁₂′ in the light guide device 720) with respectto the X direction or the optical axis AX of the image light GL02 at oneend and an angle θ₁₃ (θ₁₃′ in the light guide device 720) with respectto the X direction or the optical axis AX of the image light GL03 at theother end have substantially equal sizes and are in opposite directions.In other words, the image lights are emitted to the eye EY in a state inwhich the image lights have symmetry with the optical axis AX as thecenter. In this way, the angle θ₁₂ and the angle θ₁₃ are equal and havesymmetry with respect to the optical axis AX. Therefore, the angle θ₁₂and the angle θ₁₃ are lateral half angles of view, which are half valuesof a lateral angle of view.

As already explained, the first reflection surfaces 2 a or the secondreflection surfaces 2 b included in a group of the reflection units 2 chave the fixed pitch and are parallel to one another. Consequently,image lights, which are virtual image lights, made incident on the eyeEY of the observer can be set uniform and deterioration in the qualityof an image to be observed can be suppressed. A specific numerical valuerange of the pitches PT, which is a space among the reflection units 2 cincluded in the angle converting section 723, is set to 0.2 mm or more,more desirably, 0.2 mm to 1.3 mm. Since the pitches PT are in thisrange, it is possible to prevent image lights that should be extractedfrom being affected by diffraction in the angle converting section 723and prevent cross stripes due to the reflection units 2 c form beingconspicuous to observers.

When the light guide member 721 explained above is used, an anglecharacteristic of light beam capturing of image lights emitted from theliquid crystal display device 32 and passed through the projectionoptical system 12 is different in the longitudinal direction and thelateral direction. Concerning the longitudinal first direction D1 (the Ydirection), like the tendency or the characteristic shown in FIG. 6A andthe like, image light closer to the peripheral section more tends totilt to the outer side to be captured. On the other hand, concerning thelateral second direction D2 (the X direction), for example, a tilt angleof image light in an overlapping section of images having differentnumbers of times of reflection on the first and second reflectionsurfaces 21 a and 21 b tends to be large. In other words, image lightcloser to the center less tends to tilt to the inner side to becaptured. It is necessary to estimate, with simulation or the like, foreach screen position, a peak direction in which image light is captured.

In the case of the virtual image display apparatus 100 according to theseventh embodiment, like the virtual image display apparatus 100according to the first embodiment, desired directivity can be impartedto image light by the image forming device 10 including theoptical-directivity changing section 38. Consequently, even if the tiltof the effective image light ML emitted from the liquid crystal displaydevice 232 and effectively captured into the eye EY of the observer hasdeviation to correspond to a position or an area on a screen, it ispossible to form the image light ML having directivity corresponding tothe deviation. It is possible to suppress occurrence of luminance spotsto improve efficiency of use of illumination light.

Eighth Embodiment

A virtual image display apparatus according to an eighth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the seventh embodiment. Unless specifically explained, thevirtual image display apparatus is the same as the virtual image displayapparatus 100 according to the seventh embodiment.

In the case of this embodiment, concerning the lateral second directionD2 (the X direction), luminance spots are suppressed to a low level.Therefore, concerning only the longitudinal first direction D1 (the Ydirection), the directivity of the image light ML is controlled andoccurrence of luminance spots is suppressed to improve efficiency of useof illumination light.

In the image display device 11 shown in FIG. 22A, an optical-directivitychanging section 838 is a prism array sheet divided into, for example,three in the longitudinal Y direction. The optical-directivity changingsection 838 has slender belt-like first to third areas AR1, AR2, and AR3in the lateral Z direction. An emission side of the optical-directivitychanging section 838 is a deflecting surface 38 a that is a saw-teethlike and a step like. The first area AR1 is a flat sheet and arranged inthe center. The second area AR2 is a prism array sheet and arranged onthe upper side (the +Y side). The third area AR3 is a prism array sheetand arranged on the lower side (the −Y side). The first area AR1 is alayer-like or a flat plate-like and causes illumination light tosubstantially directly pass. The second area AR2 has a prism arrayextending in the lateral direction (the X direction) and bendsillumination light incident from the backlight guide section 31 b to theouter side (the +Y side). The third area AR3 also has a prism arrayextending in the lateral direction (the Z direction) and bendsillumination light incident from the backlight guide section 31 b to theouter side (the −Y side).

As shown in FIGS. 22B to 22D, the second area AR2 of theoptical-directivity changing section 838 has a non-uniform prism array,the wedge angle ω of which gradually increases toward the upper side(the +Y side). The illumination lights IL uniformly emitted from thebacklight guide section 31 b are given the tilt angle ε by bending whenthe illumination lights IL pass through the deflecting surface 38 a ofthe second area AR2 and are made incident on the liquid crystal displaydevice (the image-light forming section) 32 shown in FIG. 20A. The tiltangle ε is equivalent to a main direction of a light distribution of theillumination lights IL and gradually increases from the lower side tothe upper side as shown in the examples of respective areas AR21, AR22and AR23 included in the second area AR2. Specifically, a lightdistribution or a light distribution characteristic after passagethrough the second area AR2 has directivity in which an angle in themain direction (the direction of the luminance center) increases in aposition on the upper side (the +Y side) farther away from the opticalaxis AX (i.e., closer to the area section (the peripheral section) AR21at the upper end). On the other hand, the first area AR1 does not have aprism array. The illumination lights IL emitted from the backlight guidesection 31 b is made incident on the liquid crystal display device (theimage-light forming section) 32 while keeping a light distribution or alight distribution characteristic. Although not shown in the figures,the third area AR3 has a structure same as that of the second area AR2but is vertically reversed. Specifically, the third area AR3 has anon-uniform prism array, the wedge angle ω of which gradually increasestoward the lower side (the −Y side). The illumination lights ILuniformly emitted from the backlight guide section 31 b are given thelarger tilt angle ε on the lower side than on the upper side when theillumination lights IL pass through the third area AR3 and are madeincident on the liquid crystal display device 32.

In the above explanation, bending, i.e., deflection of the illuminationlights IL by the optical-directivity changing section 838 deflects theillumination lights IL further to the outer side from the center towardthe peripheral section concerning the longitudinal direction, i.e.,diffuses the illumination lights IL to the outer side as a whole. Inother words, a distribution of the tilt angle ε concerning bending inthe longitudinal direction of the illumination lights IL by theoptical-directivity changing section 838 corresponds to the anglecharacteristic of light beam capturing shown in FIG. 6B. Consequently,the liquid crystal display device 32 is illuminated by the illuminationlights IL having the tilt angle ε corresponding to the emission angle μof the image lights FL emitted from the liquid crystal display device 32and effectively utilized for virtual image formation. In other words, itis possible to substantially match the emission angle μ equivalent tothe luminance center of the effective image lights FL from the liquidcrystal display device 32 and the tilt angle ε equivalent to theluminance center of the illumination lights IL from the illuminatingdevice 31. In this way, the image lights FL emitted from the respectivepositions of the liquid crystal display device 32 and effectivelyutilized are high-luminance components. Consequently, illumination lightis not wastefully used and luminance spots of a virtual image can bereduced.

In the above explanation, in a section close to the first area AR1 inthe second area AR2, the wedge angle ω is set close to zero. This makesit possible to prevent luminance spots from occurring in a joint of boththe areas AR1 and AR2. If a prism array is provided in the first areaAR1 as well, it is possible to surely prevent luminance spots fromoccurring around the center in the longitudinal direction and furtherimprove light use efficiency.

In the above explanation, the wedge angle ω continuously changes in thesecond and third areas AR2 and AR3. However, the wedge angle ω can alsobe changed stepwise. Specifically, in both the areas AR2 and AR3, it isalso possible to further form plural divided areas in the Y direction,fix the wedge angle ω in each of the divided areas, and set the wedgeangle ω different between the divided areas adjacent to each other.

FIG. 23A is a diagram for explaining a two-dimensional luminancedistribution of image lights of a virtual image type formed by thevirtual image display apparatus 100 according to the eighth embodiment.FIG. 23B is a diagram for explaining a two-dimensional luminancedistribution of image lights of a virtual image type formed by a virtualimage display apparatus according to a comparative example. As it isevident when both the figures are compared, in the case of the virtualimage display apparatus 100 according to this embodiment, occurrence ofluminance unevenness is substantially reduced. The virtual image displayapparatus according to the comparative example has a structure same asthe structure of the virtual image display apparatus 100 according tothis embodiment. However, the virtual image display apparatus accordingto the comparative example is different from the virtual image displayapparatus 100 in that the optical-directivity changing section 838 isnot provided on the light emission side of the illuminating device 31.

FIG. 23C is a graph showing a luminance distribution in the Y directionalong a B-B cross-section of image lights formed by the virtual imagedisplay apparatus 100 according to this embodiment. FIG. 23D is a graphshowing a luminance distribution in the Y direction along a B-Bcross-section of image lights formed by the virtual image displayapparatus according to the comparative example. As it is evident whenboth the graphs are compared, in the case of the virtual image displayapparatus 100 according to this embodiment, a luminance distribution inthe longitudinal Y direction is uniform at relatively high luminance.

As explained above, with the virtual image display apparatus 100according to the eighth embodiment, the optical-directivity changingsection 838 forms a non-uniform distribution concerning the directivityof image lights emitted from the angle converting section 723,specifically, a distribution in which the tilt angle ε graduallyincreases in the periphery in the longitudinal direction. Therefore,when the emission angle μ of a light beam emitted from the liquidcrystal display device and effectively captured into the eye EY of theobserver gradually increases according to a position in the Y directionof the liquid crystal display device 32, it is possible to match thedirectivity of image lights to such an angle characteristic of lightbeam capturing into the eye EY. It is possible to suppress occurrence ofluminance spots to improve efficiency of use of illumination light.

In this embodiment, instead of incorporating the optical-directivitychanging section 38 in the illuminating device 31, as in the second orthird embodiment, the optical-directivity changing section 138 or 238can be incorporated in the liquid crystal display device (theimage-light forming section) 132 or 232.

Ninth Embodiment

A virtual image display apparatus according to a ninth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the seventh embodiment. Unless specifically explained, thevirtual image display apparatus is the same as the virtual image displayapparatus 100 according to the seventh embodiment.

As shown in FIGS. 24A and 24B, in the case of this embodiment, an angleconverting section 923 of the light guide member 721 has a structure inwhich a large number of image light reflection surfaces 2 d are arrayedin the X direction at a predetermined pitch. The image light reflectionsurfaces 2 d extends in a belt shape in a longitudinal direction set inthe Y direction, i.e., a main light guide direction, which is adirection extending perpendicularly to the −X direction in which theimage light reflection surfaces 2 d are arrayed. The image lightreflection surfaces 2 d are parallel to one another and are formed atthe same angle τ with respect to the second reflection surface 21 b. Theimage light reflection surface 2 d is a partial reflection surface thattransmits a part of light components of image light and reflects theremainder according to adjustment of reflectance. The image lightreflection surfaces 2 d adjacent to each other are connected by aboundary section 2 e not having a function of a reflection surface orthe like for extracting image light. As a result, the image lightreflection surfaces 2 d are periodically repeatedly arrayed and extendin parallel to one another along the main light guide direction, i.e.,the Z direction in a separated state. The image light reflectionsurfaces 2 d are formed by, for example, applying film formation such asaluminum vapor deposition to one slope of a V groove of a base.Thereafter, the image light reflection surfaces 2 d are embedded in thelight guide member 721 by filling resin.

As shown in FIG. 24A, after passing through the angle converting section923 plural times, the image light GL02 totally reflected on the firstand second reflection surfaces 21 a and 21 b of the light guide member721 at the minimum reflection angle γ⁻ reaches the peripheral section 23h at the end of the depth side (the −X side) in the angle convertingsection 923 and is emitted as parallel light beams from the lightemission surface OS to the eye EY at an angle θ₁₂ with respect to theoptical axis AX of the eye EY according to reflection in the peripheralsection 23 h. On the other hand, as shown in FIG. 24B, the image lightGL03 totally reflected on the first and second reflection surfaces 21 aand 21 b of the light guide member 721 at the maximum reflection angleγ₊ reaches the peripheral section 23 m at the end of the entrance side(the +X side) in the angle converting section 923 and is emitted asparallel light beams from the light emission surface OS to the eye EY atan angle θ₁₃ with respect to the optical axis AX of the eye EY accordingto reflection in the peripheral section 23 m.

In this embodiment, instead of incorporating the optical-directivitychanging section 38 or 838 in the illuminating device 31, as in thesecond or third embodiment, the optical-directivity changing section 138or 238 can be incorporated in the liquid crystal display device (theimage-light forming section) 132 or 232.

Tenth Embodiment

A virtual image display apparatus according to a tenth embodiment isexplained below. The virtual image display apparatus according to thisembodiment is a modification of the virtual image display apparatus 100according to the seventh embodiment. Unless specifically explained, thevirtual image display apparatus is the same as the virtual image displayapparatus 100 according to the seventh embodiment.

As shown in FIG. 25, the virtual image display apparatus 100 includes ahologram element 1025 instead of the prism section PS and the mirrorlayer 25 (see FIG. 2A). In this case, the image display device 11includes, as the illuminating device 31, for example, an illuminatingdevice incorporating a light source 1031 a including an LED thatgenerates light beams of three colors. The hologram element 1025 isbonded to an extended surface of the second reflection surface 21 b atan incident side end of the light guide member 721. The hologram element1025 includes a hologram layer of a three-layer structure correspondingto the three colors generated by the light source 1031 a. Consequently,the hologram element 1025 functions as an imaginary mirror formed nearthe second reflection surface 21 b at the entrance side end and has afunction of reflecting respective color lights from the image displaydevice 11 in a desired direction. In other words, the hologram element1025 enables adjustment of a reflecting direction of image light. It ispossible to efficiently capture the image light into the light guidemember 721 using the hologram element 1025.

A hologram element can also be used instead of the angle convertingsection 723 (see FIG. 21A). On the third reflection surface 21 c and thefourth reflection surface 21 d of the light guide member 721 of thelight guide device 720, a hologram element can also be used instead of amirror or a half mirror.

Others

The invention is explained above according to the embodiments. However,the invention is not limited to the embodiments and can be carried outin various forms without departing from the spirit of the invention. Forexample, modifications explained below are possible.

In the first to third embodiments and the like, the emission angles ofthe image lights FL or the image lights GL tilt larger outwards as theimage lights FL or the image lights GL is further away from the centerof the liquid crystal display device 32 in the up down direction and anemission position tilts larger inwards as the image lights FL or theimage lights GL travel from the left and right to the center and theemission position becomes smaller. However, the method of the inventioncan also be used when the projection optical system 12 and the lightguide device 20 having an angle characteristic of light beam capturingdifferent from such a tendency are used. For example, when the lightguide device 20 guides image lights in the longitudinal direction ratherthan the lateral direction, an emission angle of the image lights FL hasa tilt characteristic in which the length and the width areinterchanged. Therefore, in this case, the length and the width are alsointerchanged in a light distribution characteristic given by theoptical-directivity changing sections 38, 138, 238, and the like. Thesame holds true for the seventh embodiment. When the light guide device720 guides image lights in the longitudinal direction rather than thelateral direction, the length and the width are also interchanged in alight distribution characteristic given by the optical-directivitychanging section 38.

In the embodiment, the optical-directivity changing sections 38, 138,and 238 are the tabular members. However, the optical-directivitychanging sections 38, 138, and 238 can be replaced with thick lenses,prisms, or diffractive optical elements. When the optical-directivitychanging section is formed of the diffractive optical element, a degreeof freedom of adjustment of directivity is improved.

In the eighth embodiment, the optical-directivity changing section 838includes the first to third areas A1, A2, and A3 divided into three inthe longitudinal Y direction. However, the optical-directivity changingsection 838 can be divided into four or more in the longitudinaldirection. The optical-directivity changing section 838 can be dividedinto plural areas in the lateral X direction as well to set differentprism shapes in the respective areas.

In the embodiments, the prism array 72 a, the micro lens array 273 a,and the like are used. However, a diffractive optical element and thelike can be used instead of the prism array 72 a, the micro lens array273 a, and the like.

In the second and third embodiments, although not specificallyexplained, a phase-difference compensation plate can be inserted betweenthe liquid crystal panel 51 and at least one of the pair of polarizationfilters 52 a and 52 b to realize improvement of contrast.

In the above explanation, the transmissive liquid crystal display device32 and the like are used as the image-light forming section. However,the image-light forming section is not limited to the transmissiveliquid crystal display device and various liquid crystal display devicescan be used. For example, a reflective liquid crystal display device canalso be used. A digital micro mirror device and the like can also beused instead of the liquid crystal display device 32.

In the above explanation, in the first and second reflection surfaces 21a and 21 b, a mirror, a half mirror, or the like is not applied on thesurfaces and image lights are totally reflected and guided by aninterface with the air. However, the total reflection in the inventionincludes reflection performed by forming a mirror coat or a half mirrorfilm over the entire first and second reflection surfaces 21 a and 21 bor a part of the first and second reflection surfaces 21 a and 21 b. Forexample, on the premise that an incident angle of image lights satisfiesa total reflection condition, a mirror coat or the like is applied tothe entire first and second reflection surfaces 21 a and 21 b or a partof the first and second reflection surfaces 21 a and 21 b andsubstantially all the image lights are reflected. The total reflectionincludes the reflection in this case. If image lights having sufficientbrightness can be obtained, the entire first and second reflectionsurfaces 21 a and 21 b or a part of the first and second reflectionsurfaces 21 a and 21 b may be coated by a mirror having sometransparency.

In the above explanation, the light incident surface IS and the lightemission surface OS are arranged on the same plane. However, thearrangement of the light incident surface IS and the light emissionsurface OS is not limited to this. For example, the light incidentsurface IS can be arranged on a plane same as the first reflectionsurface 21 a and the light emission surface OS can be arranged on aplane same as the second reflection surface 21 b.

In the above explanation, the light guide member 21 extends in thelateral direction in which the eye EY is present. However, the lightguide member 21 can extend in the longitudinal direction. In this case,the optical panel 110 is arranged in parallel rather than in series.

In the above explanation, the virtual image display apparatus 100 isspecifically explained as the head-mounted display. However, the virtualimage display apparatus 100 can be modified into a head-up display.

In the virtual image display apparatus 100 according to the embodiments,the one set of display devices 100A and 100B (specifically, the imageforming devices 10, the light guide devices 20, etc.) are provided tocorrespond to both the right and left eyes. However, for example, theimage forming device 10 and the light guide device 20 may be providedonly for one of the right and left eyes to view an image with one eye.

In the embodiments, the first optical axis AX1 passing through the lightincident surface IS and the second optical axis AX2 passing through thelight incident surface IS are parallel. However, the optical axes AX1and AX2 can be nonparallel.

In the embodiments, the display luminance of the liquid crystal displaydevice 32 is not specifically adjusted. However, the display luminancecan be adjusted according to a range and an overlap of the projectedimages IM1 and IM2 shown in FIG. 5B.

In the embodiments, the reflectance of the half mirror layer 28 providedon the fourth reflection surface 21 d of the light guide member 21 isset to 20% to give priority to see-through. However, the reflectance ofthe half mirror layer 28 can be set to 50% or more to give priority toimage lights. The half mirror layer 28 does not need to be formed onlyin a necessary area in a part of the fourth reflection surface 21 d andcan be formed over the entire surface of the fourth reflection surface21 d. The half mirror layer 28 can be formed on the third surface 23 cof the light transmission member 23 as well.

The pitches PT of the array of the reflection units 2 c included in theangle converting section 723 are not always the same among the firstreflection surfaces 2 a and may be different to some extent.

In the above explanation, the see-through type virtual image displayapparatus is explained. However, the angle converting section 723 andthe like can be applied to virtual image display apparatuses of typesother than the see-through type. When it is unnecessary to observe anexternal image, the optical reflectance of the first and secondreflection surfaces 2 a and 2 b can be set to about 100%.

In the above explanation, tilt angles of the mirror layer 25 and theslope RS included in the prism section PS are not specifically referredto. However, in the invention, the tilt angles of the mirror layer 25and the like can be set to various values with respect to the opticalaxis AX according to an application and other specifications.

In the above explanation, the V groove formed by the reflection units 2c is shown as having a pointed end. However, the shape of the V grooveis not limited to this and may be a flat cut end or a rounded end.

In the above explanation, the light guide device 20 or 720 including thelight incident section B1, the light guide section B2, and the lightemission section B3 is used. However, in the light incident section B1and the light emission section B3, a plane mirror does not need to beused. A lens-like function can be imparted to the light incident sectionB1 and the light emission section B3 by a spherical or aspherical curvedsurface mirror.

Further, as shown in FIG. 26, a prism or block-like relay member 1125separated from the light guide section B2 can be used as the lightincident section B1. A lens-like function can be imparted to an incidentand emission surface and a reflection inner surface of the relay member1125. In the light guide member 21 included in the light guide sectionB2, the first and second reflection surfaces 21 a and 21 b thatpropagate the image lights GL through reflection are provided. However,the reflection surfaces 21 a and 21 b do not need to be parallel to eachother and can be curved surfaces.

The entire disclosure of Japanese Patent Application Nos. 2010-228183,filed Oct. 8, 2010 and 2011-174638, filed Aug. 10, 2011 are expresslyincorporated by reference herein.

1. A virtual image display apparatus comprising: an image display devicethat forms image light; a projection optical system that forms a virtualimage with the image light emitted from the image display device; alight guide device including a light incident section that captures theimage light passed through the projection optical system into an insideof the light incident section, a light guide section that guides theimage light captured from the light incident section using totalreflection on first and second reflection surfaces extending while beingopposed to each other, and a light emitting section that extracts theimage light passed through the light guide section to an outside; and anoptical-directivity changing section that changes directivity of theimage light emitted from the image display device and forms anon-uniform distribution
 2. The virtual image display apparatusaccording to claim 1, wherein the optical-directivity changing sectionbends, concerning a first direction, light at a different angleaccording to a position of the image display device.
 3. The virtualimage display apparatus according to claim 2, wherein theoptical-directivity changing section bends, concerning a seconddirection perpendicular to the first direction, light at a differentangle according to the position of the image display device.
 4. Thevirtual image display apparatus according to claim 3, wherein, in theoptical-directivity changing section, a light distributioncharacteristic, which is an angle distribution of directivity, isdifference concerning the first direction and the second direction. 5.The virtual image display apparatus according to claim 1, wherein theimage display device includes an illuminating device and an image-lightforming section that controls light from the illuminating device andforms image light.
 6. The virtual image display apparatus according toclaim 5, wherein the illuminating device includes a light emittingsection and a backlight guide section that spreads a light beam from thelight emitting section in a surface light source shape, and theoptical-directivity changing section is arranged between the backlightguide section and the image-light forming section.
 7. The virtual imagedisplay apparatus according to claim 5, wherein the illuminating deviceincludes a surface-light-source-like light emitting section, and theoptical-directivity changing section is arranged between thesurface-light-source-like light emitting section and the image-lightforming section.
 8. The virtual image display apparatus according toclaim 6, wherein the optical-directivity changing section is at leastone of a prism array sheet, a Fresnel lens, a diffractive opticalelement, and a micro lens array.
 9. The virtual image display apparatusaccording to claim 6, wherein the optical-directivity changing sectionis bonded to the backlight guide section or thesurface-light-source-like light emitting section and integrated with thebacklight guide section or the surface-light-source-like light emittingsection.
 10. The virtual image display apparatus according to claim 6,wherein the optical-directivity changing section includes plural areasections for causing illumination light from the backlight guide sectionor the surface-light-source-like light emitting section to pass suchthat main directivity directions having highest luminance are differentfrom each other.
 11. The virtual image display apparatus according toclaim 10, wherein the optical-directivity changing section includes aprism array having different shapes to correspond to the plural areasections.
 12. The virtual image display apparatus according to claim 1,wherein the first direction corresponds to a returning directionperpendicular to the first and second reflection surfaces of the lightguide device and the second direction corresponds to a non-returningdirection parallel to the first and second reflection surfaces of thelight guide device and perpendicular to the first direction, and in atleast one of the first direction and the second direction, plural peakdirections in which luminance is a maximum are set.
 13. The virtualimage display apparatus according to claim 12, wherein plural peakdirections in which luminance is a maximum are set in the seconddirection.
 14. The virtual image display apparatus according to claim 5,wherein the optical-directivity changing section is incorporated in orexternally attached to the image-light forming section.
 15. The virtualimage display apparatus according to claim 14, wherein the image-lightforming section is an EL display element, and the optical-directivitychanging section is arranged, for example, on a light emission side of apixel portion of the EL display element.
 16. The virtual image displayapparatus according to claim 14, wherein the image-light forming sectionis a liquid crystal display element of a light-transmissive type, andthe optical-directivity changing section is arranged, for example, on atleast one of a light incident side and a light emission side of a pixelportion of the liquid crystal display element.
 17. The virtual imagedisplay apparatus according to claim 1, wherein the light guide sectionhas a first reflection surface and a second reflection surface that arearranged in parallel to each other and enable light guide by totalreflection, the light incident section has a third reflection surfaceformed at a predetermined angle with respect to the first reflectionsurface, and the light emitting section has a fourth reflection surfaceformed at a predetermined angle with respect to the first reflectionsurface.
 18. The virtual image display apparatus according to claim 1,wherein the light emitting section includes an angle converting sectionthat has plural reflection surfaces and converts an angle of the imagelight through reflection on the plural reflection surfaces to enable theimage light to be extracted to the outside.
 19. The virtual imagedisplay apparatus according to claim 18, wherein the angle convertingsection includes plural reflection units that respectively have firstreflection surfaces and second reflection surfaces formed at apredetermined angle with respect to the first reflection surfaces andare arrayed in a predetermined array direction, and the reflection unitsreflect, with the first reflection surfaces, the image light madeincident through the light guide section and further reflect, with thesecond reflection surfaces, the image light reflected by the firstreflection surfaces to thereby bend an optical path of the image lightand enable the image light to be extracted to the outside.